Monster Media 1996 #15

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F / W I N 3 . 1 1 ===================================== HEURISTIC DETECTION OF WINDOWS, WINDOWS 95 AND MACRO VIRUSES Author of F/WIN --------------- Stefan Kurtzhals Dörrenberg 42 42899 Remscheid Germany E-Mail: kurtzhal@wrcs3.urz.uni-wuppertal.de Fido: 2:2480/8849.2 United States Authorized Agent ------------------------------ Computer Virus Solutions C/O Gary Martin P.O. Box. 30802 Gahanna, Ohio 43230 Voice: (614) 337-0995 E-mail: FWIN_SUP@ix.netcom.com WWW: http://www.gen.com/fwin TABLE OF CONTENTS ================= 1.0 OVERVIEW OF F/WIN 1.1 Tips for using this documentation 1.2 What "Heuristic" detection is 1.3 What F/WIN can detect - for Non-technical users 1.4 What F/WIN can detect - for Technical users 1.5 What F/WIN can clean - for Non-Technical users 1.6 What F/WIN can clean - For Technical users 1.7 False alarms 2.0 HOW TO USE F/WIN 2.1 From a DOS prompt 2.2 From Windows 3.x 2.3 From Windows '95 2.4 From OS/2 Warp 2.5 Choices F/WIN provides when a suspected virus is found 2.6 Situations in which F/WIN should N-O-T be run 3.0 HOW TO ORDER A REGISTERED VERSION OF F/WIN 3.1 Extras in the registered version 3.2 In Germany 3.3 In the United States 3.4 In other countries 3.5 Stefan Kurtzhals PGP public key (Germany) 3.6 Gary Martin's PGP public key (USA) 4.0 WINDOWS EXE VIRUSES 4.1 For NON-technical readers 4.1.1 F/WIN's detection of 4.2 For Technical readers 4.2.1 F/WIN's detection of 5.0 MACRO VIRUSES 5.1 What they are 5.2 History of 5.3 Why they pose such a threat to your data 5.4 F/WIN's detection of 5.5 How the viruses are removed 6.0 F/WIN MESSAGES FOR WINDOWS VIRUSES 6.1 Possible 16-bit virus (NE-EXE) 6.2 Possible 32-bit virus (PE-EXE) 7.0 F/WIN MESSAGES FOR MACRO VIRUSES 7.1 - A backup has been created: 7.2 - Attempt to backup file before cleaning failed! 7.3 - Changes DOS attributes of other files 7.4 - Contains # macros (# bytes) 7.5 - Contains macros but is not named .DOC 7.6 - Contains execute-only macros (encrypted macros) 7.7 - Contains macro shortcuts 7.8 - Contains macros 7.9 - Copy macros into the global template ('CopyMacro') 7.10 - Deletes other files! (Kill) 7.11 - Disables NORMAL.DOT write access warnings 7.12 - Enables the quick save option 7.13 - Execute other DOS or Windows programs! (Shell) 7.14 - F/WIN can not check Microsoft Word 2.0 documents! 7.15 - F/WIN can not clean this file safely! 7.16 - has been moved to: 7.17 - Might contain suspicious macros 7.18 - Might contain an antivirus-macro (please verify!) 7.19 - Reenables auto macro processing 7.20 - Seems to be infected with a macro virus! 7.21 - Seems to contain a trojan macro! 7.22 - System macros: 7.22.1 AUTOCLOSE 7.22.2 AUTOEXEC 7.22.3 AUTONEW 7.22.4 AUTOOPEN 7.22.5 FILEEXIT 7.22.6 FILENEW 7.22.7 FILESAVE 7.22.8 FILESAVEAS 7.22.9 TOOLSMACRO 7.23 - The file has been moved to: 7.24 - The macros within this file are disabled! 7.25 - This document is internally fragmented. The repair could have failed! 7.26 - Uses macro 'FileSaveAs' 7.27 - Uses 'Organize .Copy' to copy macros' 7.28 - Writes into other files directly (Write) 8.0 COPYRIGHT, LICENSE TERMS AND DISCLAIMER 9.0 GLOSSARY OF TERMS USED IN THIS DOCUMENTATION 1.0 OVERVIEW OF F/WIN ================================================================= 1.1 Tips for using this documentation ----------------------------------------------------------------- a. Do a character string search for what you're looking for. This may be the fastest way to locate the needed information. b. Check the Table of Contents, then do a character string search on the section number. c. In several sections, there are two versions of the documentation. One is for novice users, the other for people who are fairly familiar with virus and other technical terminology. We thought about splitting these two types of documentation up into different files, but decided against doing it. We suspect that many less experienced users will want to take a crack at trying to understand the technical explanations, and keeping them grouped together by topic will make that easier to do. d. In the novice sections, there are key words and phrases that appear in all uppercase, and are enclosed in brackets {}. These terms are defined in the Glossary. 1.2 What "Heuristic" detection is ----------------------------------------------------------------- F/WIN doesn't use {scan strings} to detect viruses. This method is fast but won't detect {unknown viruses}. Instead, it uses heuristic scanning techniques. Scan strings searches look for strings (combinations) of characters that are unique to a particular virus. Heuristic analysis look for any kind of dangerous code or virus like code, regardless of what particular virus it may belong to, or what the macro name is. For instance, the <Winword.Concept> virus is typically located by searching for the macro names that it uses. Those macro names are: AAAZAO AAAZFS AutoOpen Payload When scan string scanners find these macro names, they correctly flag the document as being infected with this virus. However, what if someone were to copy these macros into another document and slightly modify them? Well, we did just that and the resulting 'new' virus was completely undetectable by a lot of the common virus scanners on the market that we tested. Only F/WIN was able to detect it, because it searches for macro viruses in a completely different way. In this example, F/WIN would look for potentially dangerous commands within each macro and flag them. It also notifies the user of any macros that could be run automatically, such as those that are run when files are opened, closed, saved, etc. Macro viruses often use these automatic or "system" macros to spread themselves, or to carry out destructive activities. These are the messages you would see when F/WIN's heuristic scanner finds the <Winword.Concept> virus: - Contains macros - System macros: AUTOOPEN - Copy macros into the global template 'CopyMacro' - Uses macro 'FileSaveAs' Seems to be infected with a macro virus ANY macro that contained the kind of coding flagged above would be flagged as being possibly virus infected, not just <Winword.Concept>. So even though we changed the virus internally, F/WIN was still able to locate the virus using these heuristic scanning techniques. These messages are explained in more detail in sections 6.0 and 7.0. 1.3 What F/WIN can detect - for Non-Technical users ----------------------------------------------------------------- F/WIN uses heuristic scanning techniques to detect: a. Macro viruses in Microsoft Word release 6.0 and 7.0 documents. The current release will not detect viruses or trojans in Word 2.0 files, but that's a feature we'll be adding later. It doesn't matter what the file is called. F/WIN will scan all files that appear in the selected directory and all of its sub-directories looking for viruses. So if you have a virus in a Word document you've called "PAYROLL.WK1", F/WIN will find it just as easily as if you had named it "PAYROLL.DOC" or "PAYROLL". F/WIN CAN N-O-T DETECT THE PRESENCE OF MACRO VIRUSES IN MICROSOFT WORD DOCUMENTS THAT ARE ENCRYPTED WITH A PASSWORD. If you suspect that a password protected document is infected, copy the document onto a PC where it won't matter if a virus destroys data and open and scan it there. Or send it to your regular anti-virus company, or to the author of F/WIN to check and clean it. b. A special kind of virus that infects EXE files for Windows or Windows '95. "EXE" files are executable files and usually have the file extension ".EXE" or ".DLL". The ".EXE" file extension (last three characters of the file name) is reserved by DOS and Windows for executable files only. DOS EXE files are structured differently than Windows EXE files. F/WIN locates viruses that have infected Windows executable files only. (Exception: the DOS executables infected by <NE.Ph33r> will also be detected, but not with heuristics.) 1.4 What F/WIN can detect - for Technical users ----------------------------------------------------------------- Windows executables are quite different from the normal DOS EXE files. Windows 3.x uses the NE-EXE format (New Executable) and Windows 95 uses PE-EXE (Portable Executable) which is also used by Windows NT. Because the new file structures are so different from the standard DOS EXE format, most virus coders never manage to write real Windows viruses. However, some virus coders from Australia finally managed to write a fully functional Windows 3.x virus, namely <NE.Winsurfer> and later <NE.Ph33r>. The used infection scheme is much more "advanced" in some ways so that it's likely that other virus coders will copy it. NE-EXE viruses are detected by analyzing the program header of any NE-EXE file found. The NE-EXE viruses modify the programs in a special way which allows a reliable detection of this virus type. It doesn't matter if the virus is polymorphic, F/WIN doesn't check any program code at all! In other words, it can detect, in a general or generic way, that a virus is likely present. But F/WIN can't tell you exactly which virus it is. Still, this feature of F/WIN is quite valuable because of it's ability to detect unknown viruses, and let you know that you have a problem sooner, rather than later. It detects specifically the infection scheme that <NE.Winsurfer> and <NE.Ph33r> use. These were the first really "functional" Windows executables viruses, and their techniques will most likely be copied by other virus authors. F/WIN also detects the only known PE-EXE virus for Windows 95 using a similar approach. Because only one PE-EXE virus exist so far, it really can't be said how good the heuristic detection is, but F/WIN will of course be updated in order to catch newer variants if they are undetectable by the current heuristic approach. All three known <Boza> variants are detected by F/WIN. F/WIN detected all the known NE-EXE and PE-EXE viruses which use the described infection mechanism. If however you should happen to come across one that is not detected by F/WIN, please e-mail a copy of it to the author of F/WIN for analysis. See SENDVIR.TXT for more information. The macro virus detection is more complicated. Because we weren't able to get a technical description of the DOC format used by Microsoft Word (how macros are stored within each document or template), F/WIN has to scan the whole DOC file to find the macro list and definitions. F/WIN checks for the existence of auto macros (such as AutoExec, AutoOpen, AutoClose, FileExit), encrypted macros, renamed templates (templates are normally named ".DOT"), standard virus commands (like MacroCopy or FileSaveAs) and dangerous commands (like Shell, Kill or Write). Any macro that is found to contain one or more of these commands will be flagged as being possibly virus infected. F/WIN checks unencrypted macros as well as encrypted (execute-only) ones. F/WIN CAN N-O-T DETECT THE PRESENCE OF MACRO VIRUSES IN MICROSOFT WORD DOCUMENTS THAT ARE ENCRYPTED WITH A PASSWORD (the whole document is encrypted, not just the macros). 1.5 What F/WIN can clean - for Non-Technical users ----------------------------------------------------------------- Macro viruses in Microsoft Word documents F/WIN doesn't remove suspected viruses without asking the user or taking some precautions. First it makes a backup copy of the file before disinfecting it. The backup file will have the same file name, except that it will have a file extension (end with) .VIR. So an infected file named PAYROLL.WK1 would have a backup file called PAYROLL.VIR. If there are more files with the same name, F/WIN will use file extensions like ".VI1", ".VI2" etc.. Next F/WIN overwrites the virus's macro code with harmless code and wipes the offending macro names from the macro list if you choose the 'Clean' option. Because the DOC format is so complex, the cleaning process may fail. In this case, you can then try a different approach by restoring the backup copy and using the 'Wipe macro names' option. DON'T FORGET TO REMOVE ALL THE .Vnn FILES WHEN YOU'RE FINISHED WITH THEM. We suggest also using a product like Norton Utilities WIPEINFO.EXE to wipe the FREE SPACE (not the whole drive) on the entire hard drive after all macro virus files are cleaned and removed. If the files are just deleted, in many cases, they can simply be undeleted and reused by someone with bad intentions. Wiping all the free space on the entire hard drive will prevent someone from recovering a virus infected file by undeleting it, or by using a disk editor. Windows EXE files ----------------- F/WIN can clean most of the known Windows 3.x (NE-EXE) and Windows 95 (PE-EXE) viruses like Boza, Ph33r, Winlame, Wintiny and Tentacle. The cleaning is generic which means that F/WIN will also clean most of the future viruses which use the same infection scheme. 1.6 What F/WIN can clean - for Technical users ----------------------------------------------------------------- Macro viruses in Microsoft Word documents ----------------------------------------- F/WIN doesn't remove suspected viruses without asking the user or taking some precautions. First it makes a backup copy of the file before disinfecting it. Actually, F/WIN won't start the cleaning process if it can't create the backup file! The backup file will have the same file name, except that it will have a file extension (end with) ".VIR" (if there are duplicate file names, F/WIN will use ".VI1", ".VI2" etc.). So an infected file named PAYROLL.WK1 would have a backup file called PAYROLL.VIR. Next F/WIN overwrites the virus's macro code with harmless code that does nothing and wipes the offending macro names from the macro list. If on the outside chance the cleaning process leaves it unreadable, you can then try a different approach using the backup copy and selecting 'Wipe macro names'. DON'T FORGET TO REMOVE ALL THE BACKUP FILES WHEN YOU'RE FINISHED WITH THEM. Also note that DOC files are OLE2 objects. An OLE2 object could be internally split up in several parts. Like hard disk clusters, these parts can be fragmented and worst of all, they have a slack area like real clusters. This is quite a security hole, and Microsoft already offers an update for OLE2 for Windows 95 which correctly handle this 'slack areas'. Windows .EXE files ------------------ F/WIN can detect and clean the only known PE-NE (Windows 95 virus), and any future ones that use similar infection schemes. It can also detect and clean several of the newer NE-EXE (Windows 3.x) viruses, which use the same infection scheme as Ph33r. These viruses add a relocation entry add the end of the file which is used by F/WIN to locate the original entry point of the program. The cleaning method used by F/WIN is generic and will even clean certain encrypted or polymorphic NE-EXE viruses as the relocation entry can't get encrypted by the virus. Some of the known NE-EXE viruses use other ways to store this information and can't be cleaned by the current cleaning approach of F/WIN. Please note the shareware version of F/WIN is restricted and will not clean viruses but only detects them. 1.7 False alarms ----------------------------------------------------------------- Every heuristic analysis will cause either false positives or {false negatives}. Of course this is also true for F/WIN. This means that F/WIN may flag some harmless files as infected and on the other hand will miss some of the more unusual viruses. We tried everything to keep the amount of both the false positives and negatives as low as possible, but we can't completely avoid them. Windows .EXE files ------------------ F/WIN may on rare occasions trigger a false alarm on Windows EXE files. Should you experience one, please send a copy of the file that was flagged in error to the author of F/WIN for evaluation. F/WIN will either be modified to stop triggering the false alarm, or a new file will be created listing known false alarms. So far, the most false positives were caused by device drivers or special DLLs. Microsoft Word Macro Viruses ---------------------------- After the first macro viruses appeared, the AV companies and others released some Microsoft Word .DOT and .DOC files that contained anti-virus macros which can detect and clean some of the viruses. F/WIN will flag some of the antivirus macros we tested as being possibly infected. We tested SCAN831.DOC, SCANPROT.DOT, WVFIX.DOT, AVPW10n.DOT (also AVPW10nG.DOT) and CHEKWORD.DOC. The reason F/WIN flags them is because they contain almost all of the same potentially dangerous macro commands which are sometimes found in macro viruses. It's impossible to distinguish between such an antivirus macro and a real macro virus without creating a severe security hole in F/WIN! SCANPROT.DOC, CHEKWORD.DOC and AVPW10n.DOT were all flagged as being possibly infected by a virus. However, F/WIN will produce a message that flashes in the color green alerting the user to the possibility that the document being flagged may be a legitimate anti-virus template. The text of the message is: "Might contain an antivirus-macro (please verify!)" See section 7.14 for more about this. As an example we will show here the messages that F/WIN produces when it analyzes SCANPROT.DOT: C:\MSOFFICE\WINWORD\TEMPLATE\SCANPROT.DOT - Contains macros - System macros: AUTOOPEN, AUTOCLOSE, AUTONEW - Copy macros into the global template (CopyMacro) - Uses macro 'FileSaveAs' - Execute other DOS or Windows programs! (Shell) - Writes into other files directly (Write) - Deletes other files! (Kill) - Changes DOS attributes of other files Seems to be infected with a macro virus! Might contain an antivirus-macro (please verify!) There is a small percentage of Microsoft Word users who write legitimate, useful macros that may use some of the commands that F/WIN detects. Especially the experienced user quite often uses macros to speed up the work with Winword. In general, if you know that you have not written any macros and that you've not received any documents with known macros in them, then it's highly likely that you do have a virus if F/WIN detects the presence of suspicious macro code in your Microsoft Word documents or templates. This is especially true if possible infections are detected in multiple documents. If legitimate macros are present in your environment that trigger warnings from F/WIN, make a note of what commands F/WIN is finding and flagging and make sure your macros are supposed to contain those commands. 2.0 HOW TO USE F/WIN ================================================================= In general, it's important that you don't run Microsoft Word itself at the same time as F/WIN. F/WIN is able to check already opened files, but it can't clean them because it will not get write access to such files. So, if your NORMAL.DOT or other document is infected with a macro virus, you must exit Word before running F/WIN. 2.1 From a DOS prompt ----------------------------------------------------------------- If you run F/WIN without parameters, you will be prompted to enter a drive letter which will be scanned then. There are three levels of scanning that F/WIN does for Macro viruses and trojans. It is important to understand which is right for your needs before choosing the one you want. LEVEL 0: F/WIN detects and produces warning messages for obvious virus and trojan files. However, no trojans are detected with the shareware version. All currently known Word 6.0 and 7.0 viruses are detected at this level. This is the default level of scanning when the /MODE, /PARANOID and /EXTENDED parameters are not used. This level detects viruses and trojans that are fully functional. "Fully functional" means that they contain all the components that would normally be present in a virus or trojan. The four most important criteria F/WIN uses to make this determination are: a) How likely is it that the macro code will be executed without the users knowledge or consent? If the macro code is placed into a macro called "ABC", it is quite unlikely that any user would run such a macro by accident. But if it were placed in one of the system macros like "AutoOpen" or "FileSaveAs", then it would be very easy for most users to execute the macro code without knowing they were doing it. b) Does the macro code contain any potentially destructive code? This would also include any linking to programs other than Word (i.e. running a DOS "ERASE" command). c) Can the macro(s) that are present in the document spread themselves to other files? d) Does the pattern of code in the macro(s) fit the pattern of known anti-virus macros? If 'a', 'b' and 'c' are all true, then F/WIN considers the document to be infected by "virus", because viruses by their nature spread to other files. If only 'a' and 'b' are true, then F/WIN flags the file as being possibly infected by a "trojan", because trojans don't spread. If 'd' is true, then F/WIN produces an extra message informing the user that the current file that F/WIN is producing messages for may be an anti-virus template. If it is, then they don't need to be concerned. Users are encouraged to verify for sure that such templates are being used in their environment. Don't assume that it's harmless when this extra message is produced. It could be a clever virus designed specifically to trigger this message in F/WIN for the purpose of deceiving the user. LEVEL 1: Level 1 detection does everything Level 0 does, and MORE. To use extended mode, specify either /MODE=1 or /EXTENDED. This is called "Extended Mode" Level 1 will produce warning messages even if all the conditions specified in level 0 are not met. To use LEVEL 1 scanning, use the /MODE=1 parameter. For instance, if F/WIN finds a WordBasic "Kill" command (deletes files) in an execute-only macro called "AutoOpen", at this level of scanning, it will produce a warning message that says: "Might contain suspicious macros" This message will appear only in level 1 or 2 scanning. The "Extended Mode" might cause more false positives than the standard scanning mode. LEVEL 2: Level 2 detection does everything Level 1 does, and MORE. Use the /MODE=2 or /PARANOID parameter to get the most comprehensive scanning F/WIN can deliver. For example, a template called "VIRUS.DOC" with a macro "Harmless" which contains a single KILL will be flagged by F/WIN if you use the Paranoid mode. In general, F/WIN needs much less criteria to flag a document as being suspicious. Especially very simple macro trojans can only be detected in this mode but it will also cause much more false positives than the Normal or Standard scanning. If you're not sure which level to use, start with the highest level, and work your way backwards if you get a lot of false alarms. For instance: 1. Start by using /PARANOID or /MODE=2. If you get too many false alarms, then: 2. Use /MODE=1 or /EXTENDED. If you still get too many false alarms, then: 3. Run F/WIN without specifying either the /MODE=n, /EXTENDED or /PARANOID commands. The syntax for F/WIN is as follows. Parameters enclosed in [ ]'s are optional: FWIN path [/?] [/H] [/DOC] [/REPORT=Name] [/EXTENDED] [/PARANOID] [/MODE=n] [/RENAMEALL] [/WIPEALL] [/CLEANALL] [/IGNOREALL] [/MOVE=directory] [/TROJAN] path The directory and all of its sub-directories to be scanned. Specify just the drive name if the entire drive is to be scanned. Wild-cards in the dataset name are not allowed. You may specify only one drive or path name at a time. CD-ROM drives names may also be specified. F/WIN accepts Windows 95 long file name paths, but keep in mind that the DOS command-line only can handle 128 chars. Path names with spaces must be enclosed in quotation marks. /? or /H Will display a short help screen. /DOC F/WIN scans only .DOC and .DOT files. The default is to scan ALL files. This will increase the scan speed, but F/WIN will only detect macro viruses with this option enabled. /REPORT=... The path and file name for a text file that contains a report of the files that F/WIN checked. The report option is only available in the registered version. For instance: /REPORT=C:\FWINCDRV.RPT. /MODE=n Enables the advanced scanning modes. n = 1 : Extended mode. This is the same as using the /EXTENDED parameter. n = 2 : Paranoid. This is the same as using the /PARANOID parameter. /EXTENDED By default, F/WIN checks macros carefully and will try to minimize the chance of false positives. However, this keeps F/WIN from detecting some trojan macros. If you enable the extended mode, F/WIN will also report documents which contain suspicious macros but doesn't seem to contain a complete macro virus or trojan. /EXTENDED is equal to /MODE=1 and only available in the registered version. /PARANOID By default, F/WIN checks macros carefully and will try to minimize the chance of false positives. However, this keeps F/WIN from detecting some trojan macros. If you enable the paranoid mode, F/WIN will also report macros which are only partially suspicious but will also report more false positives. /PARANOID and /MODE=2 perform exactly the same functions. The /PARANOID parameter was included because it might be easier for some users to remember than /MODE=2. If you don't use Word macros at all, /PARANOID or /MODE=2 is a very good choice. /RENAMEALL F/WIN renames all suspicious files it detects without prompting for user input. /CLEANALL By default, F/WIN prompts for what action to take on an infected file as it encounters each one. This switch tells F/WIN to not prompt for action on each file, but instead, to go ahead and remove the virus from all infected files using the "CLEAN" method. "Clean" is a deep cleaning. In additional to writing over the macro definition list, it also writes over the virus code itself. Because of internal fragmentation in Word templates, clean will sometimes not clean the document properly leaving it unreadable, or locking your PC up when trying to access the document after the clean. However, a backup of all cleaned files are made, so you can try the WIPE disinfect method instead if the CLEAN method fails (after restoring the document from the backup). Most likely, F/WIN by itself will detect that a file can't be cleaned with the "CLEAN" option and will report the message "This file can not be cleaned safely!". If this option is used, you MUST also use the /REPORT= option. /CLEANALL Can't be used with /RENAMEALL or /WIPEALL. /WIPEALL By default, F/WIN prompts for what action to take on an infected file as it encounters each one. This switch tells F/WIN to not prompt for action on each file, but instead, to go ahead and remove the virus from all infected files using the "WIPE" method. "Wipe" is a shallow cleaning. In simply writes over the the macro name and offset list. It does not write over the virus code itself like CLEAN does. However, Word will never be able to access the virus code again using this cleaning method, so it is quite effective. Since /WIPEALL only wipes the macro name and offset list, it is far less susceptible to damaging documents it disinfects. As a result, it is only on very rare occasions that F/WIN damages templates it cleans this way. /WIPEALL makes a backup copy of all modified files. If this option is used, you MUST also use the /REPORT= option. /WIPEALL Can't be used with /RENAMEALL or /CLEANALL. /IGNOREALL Like /RENAMEALL, /WIPEALL and /CLEANALL, F/WIN will not stop and prompt for user input if it detects suspicious files. When you use /IGNOREALL, the suspicious files will stay untouched. /IGNOREALL can only be used with /REPORT and can be used in DOS batch files. Using /IGNOREALL has the same affect as choosing the (Skip all) feature. /MOVE= When F/WIN removes any virus or trojan it first makes a backup copy of the infected file. By default, F/WIN makes the backup copy in the same directory as the file from which the virus/trojan was removed. For instance, if F/WIN cleaned a file in C:\WINWORD\INFECTED.DOC, it would, by default, make a backup file called C:\WINWORD\INFECTED.VIR. Also, if a file is too fragmented for F/WIN to clean it safely, F/WIN just leaves the file right where it is (it produces a message saying it can't clean the file). When the /MOVE= parameter is used, it allows the user to specify what directory backup files, and files that couldn't be cleaned appear in. F/WIN creates two sub- directories under the directory specified in the /MOVE= parameter. For instance, assume that the user wants to put all backup files into a directory called C:\FWINBKUP. Here's how the parameter would be coded: /MOVE=C:\FWINBKUP F/WIN would then create to additional sub-directories under that one. One would be called \BACKUP and the other \DAMAGE. Using this same example, this is what F/WIN would create: C:\FWINBKUP\BACKUP (backups of files that F/WIN was able to clean) C:\FWINBKUP\DAMAGE (original files that F/WIN was NOT able to clean. They literally were moved to this directory, not just copied). /TROJAN= By default, F/WIN will NOT check for trojans, only viruses. This is to help reduce the possibility of false positives. When /TROJAN is specified, F/WIN will notify users of possible harmful trojans as well as viruses. How sensitive F/WIN is to detecting trojans depends on which additional parameters are used. Currently, there are no macro trojans reported in the wild. Level 0 sensitivity (lowest): /EXTENDED, /MODE and /PARANOID NOT used. Level 1 sensitivity (medium): /EXTENDED or /MODE=1 also specified. Level 2 sensitivity (maximum): /PARANOID or /MODE=2 also specified. When using F/WIN in a DOS Batch file, it will return the following error levels that can be checked in a DOS batch file: 0 - F/WIN finished the scan without finding suspicious files. 1 - F/WIN detected suspicious files during the scan process. 252 - The evaluation version has expired. This message is referring to the fully-functional evaluation copy, not the partially functional shareware version. 253 - A wrong scan drive or path specified. 254 - An wrong command-line parameter was specified 255 - F/WIN found a companion virus which has infected F/WIN.EXE. Here are some examples of how to execute F/WIN: FWIN D: (scans the entire D: drive) FWIN "C:\MSOffice\WinWord\Template\My templates" (Scan the "My templates" subdirectory and all directories below it. Note that the parameters passed to FWIN had to be enclosed in quotes in this case because of the space that appears between "My" and "templates") FWIN A:\ /REPORT=C:\FWIN.RPT (scans the entire A: drive, and puts a report of what it found into the file C:/FWIN.RPT) FWIN D:\ /REPORT=A:\FWIN.RPT /PARANOID /DOC (scans the entire D: drive, and puts a report of what it found in A:/FWIN.RPT, and checks ONLY macros in files that end in .DOC or .DOT) FWIN C:\ /REPORT=A:\FWIN.RPT /MODE=2 /CLEANALL (scans the entire C: drive in the Paranoid mode and puts a report of what it found in A:/FWIN.RPT, and cleans all files infected with Word macro viruses or trojans.) FWIN C:\ /REPORT=C:\FWIN.RPT /MODE=1 /WIPEALL (scans the entire C: drive, and puts a report of what it found in C:/FWIN.RPT, and wipes the macro definition list from all files infected with Word macro viruses or trojans that satisfy the /MODE=1 search criteria. Also makes a backup copy of all disinfected files.) FWIN (F/WIN will prompt for which drive to scan. Just enter the letter of the drive (don't add a ':' after it). It also produces the same help information that's listed when the /H or /? parameters are used. FWIN /? (F/WIN displays help information) FWIN C:\*.DOC (will NOT work; wildcards are not valid) FWIN C: /REPORT=C:\FWIN_C.RPT /IGNOREALL (Scan the C: drive, and put the results of the scan in a file called FWIN_C.RPT on the C: drive root directory. F/WIN doesn't stop scanning for any viruses found (/IGNOREALL), just keeps scanning and only reports what is found. 2.2 From Windows 3.x ----------------------------------------------------------------- Option #1: Click on the "MS-DOS PROMPT" icon in the "MAIN" window and follow the previous instructions for running from a DOS prompt. Option #2: On the PROGRAM MANAGER screen, click on "FILE", then on "RUN". Point to where FWIN is stored, then add the appropriate parms to run it the way you want it to. For instance, in the box that says "COMMAND LINE", you would enter: "C:\FWIN C:" to scan the C: drive, assuming that FWIN was being stored in the root directory of the C: drive. In either of the above two options, F/WIN will prompt you for the path to scan if it isn't specified. 2.3 From Windows '95 ----------------------------------------------------------------- Option #1: Run it from DOS. There are three ways to get to it. First way: Click on "START" Click on "RUN" Key in the appropriate FWIN command. Use the previous instructions for running F- WIN in DOS. For instance, enter: C:\FWIN A: to scan the A: drive. Click on "OK" Second way: Click on "START" Click on "PROGRAMS" Click on "MS-DOS PROMPT" Key in the appropriate FWIN command. Use the previous instructions for running F- WIN in DOS. For instance, enter: C:\FWIN A: to scan the A: drive. Third way: Click on "START" Click on "PROGRAMS" Click on "MAIN" Click on "MS-DOS PROMPT" Key in the appropriate FWIN command. Use the previous instructions for running F- WIN in DOS. For instance, enter: C:\FWIN A: to scan the A: drive. You may also set up icons to run FWIN with from the Windows 95 Menu. In these example below, FWIN will scan the A: drive: Copy FWIN.EXE into whatever directory you want to run it from. In this example, it is run from the C:\ directory. Click on "START" Click on "SETTINGS" Click on "TASKBAR" Click on "START MENU PROGRAMS" Click on "ADD" Key in "C:\FWIN.EXE A:" in the box labeled "Command Line", then press ENTER Click on "NEXT" Key in "FWIN (scan A drive)" in the box labeled "Select a name for the shortcut", then press ENTER Click on the icon of your choice, or use the FWIN.ICO file that came with F/WIN. Click on "FINISH", then "OK" To run what you just set up: Click on "START" Click on "PROGRAMS" Click on "FWIN (scan A drive)" 2.4 From OS/2 Warp ----------------------------------------------------------------- Open an OS/2 DOS window. Then execute F/WIN exactly the same way you would as if you were running it in DOS. 2.5 Choices F/WIN provides when a suspected virus is found ----------------------------------------------------------------- If F/WIN detected a suspicious files, it will stop scanning and display some messages. At the bottom of this text you will get a display similar to the examples below: This file has suspicious structures! (32 bit virus?) Rename file? [Y]es, [N]o, [A]ll, [S]kip all : This document has suspicious structures or contents: Rename file? [Y]es, [N]o, Rename [A]ll, [C]lean file, [W]ipe macro names, [S]kip all : You choose options by pressing the letter enclosed in brackets (F/WIN will display this chars in another color). The options explained in detail: - (Rename file) [Y]es: F/WIN will rename this document to another file extension (.VIR, VI1, etc.) and will continue the search. The contents of the reported file are not changed. - (Rename file) [N]o: F/WIN will do nothing with the reported file and will continue the search normally. - (Rename) [A]ll: This and all further suspicious files will be renamed to a .VIR extension. F/WIN will not stop and prompt if it detects further files with suspicious contents. (F/WIN will rename both macro and Windows EXE viruses) - [S]kip all: The search will be continued and F/WIN will not interrupt again if it finds suspicious files. All suspicious files will remain unchanged. This feature may not be very helpful unless you also use the /REPORT option. - [C]lean: Macro viruses: F/WIN will try to clean the reported file with the full cleaning method. Before starting the cleaning process, it will create a backup of the target file. The cleaning process will get aborted if F/WIN can't create the backup file. All macros are removed from the template, not just the virus macros! Windows 3.x (NE-EXE) viruses: F/WIN will try to clean the reported file by searching the original entry point in the virus code. The virus code will be removed completely by F/WIN. If the virus can't be cleaned, F/WIN will report "This file can not be cleaned safely". - [W]ipe macro names: Like the full cleaning option, F/WIN will create a backup before trying to modify a file. Removing just the macro name and offset list from a document is much safer than CLEAN and you should use this option if you encounter problems with the full cleaning. All macros are removed from the template, not only the virus macros. This option is not available for Windows EXE viruses. 2.6 Situations in which FWIN should N-O-T be run ----------------------------------------------------------------- If you suspect that a DOS, Windows 95 or OS/2 virus is memory resident, do N-O-T run F/WIN until you are confident that the virus is no longer memory resident. If a virus is memory resident, and it's a "fast infector", running F/WIN can cause it to infect every executable file it's capable of infecting during F/WIN's scan. F/WIN is not a full-blown scanner that can check to see if DOS and Windows viruses are resident in memory. It is a specialized scanner that supplements the regular scanner you already have. Use your regular scanner to make sure there are no memory resident viruses before running F/WIN or better yet, boot from a clean system disk. These precautions are only necessary against resident DOS, Windows 95 or OS/2 file or boot sector viruses. Macro viruses are 'resident' too, but don't directly interfere with a running of those three operating systems programs. 3.0 HOW TO ORDER A REGISTERED VERSION OF FWIN ================================================================= 3.1 Extras in the registered version The following extra features will appear in the registered version that aren't active in the shareware version. a) Cleaning of all files will be activated (not just NORMAL.DOT). b) /REPORT switch will be activated c) /MODE and /PARANOID switches will be activated d) /CLEANALL and /WIPEALL will be activated 3.2 In Germany Orders can be submitted using e-mail or normal way. Please fill in the file REGISTER.TXT and send it to: Stefan Kurtzhals Dörrenberg 42 42899 Remscheid Germany E-Mail: kurtzhal@wrcs3.urz.uni-wuppertal.de The registered version will be sent either on a 3,5" disk or by PGP encrypted E-Mail. Please don't forget to add your public PGP key if you want to receive the registered version by E-Mail! You will receive a PKZIP archive which will contain the latest version of F/WIN and a personal key file. The latest German shareware version of F/WIN can be downloaded from: - HTTP://WWW.GEN.COM/FWIN - HTTP://WWW.CYBERBOX.NORTH.DE - CYBERBOX BBS (V32b: 0441-3990032, V34: 0441-3990033, ISDN: 0441-9396977) - VHM II BBS (V34/ISDN: 08638-881108) 3.3 In the United States PAYING FOR THE REGISTERED VERSION --------------------------------- Print and fill out the file ORDER.TXT, then mail to: Computer Virus Solutions Order Processing P.O. Box 30802 Gahanna, Ohio 43230 United States of America Please include a check or money-order payable to: "COMPUTER VIRUS SOLUTIONS" At this time, we are not yet set up to accept credit card orders, but we should be in the future. When we are able to accept credit card orders, there will also be a dedicated fax line to place your orders by fax. We are hoping to have that available in the middle to end of March, 1996. Watch our WWW site for news about this. HOW TO RECEIVE THE SOFTWARE AND KEY FILE ---------------------------------------- Option #1 --------- Download the shareware version from an FTP site. After receiving your payment by mail, we'll send you your unique key file which turns the shareware version into the registered version. You may receive your key file in any of the following ways: a. By mail on a floppy diskette. b. By e-mail as a PGP encrypted binary file attachment (make sure you're e-mail system allows this) c. A UUENCODE'd e-mail message (must be PGP encrypted, though) d. A PGP ASCII file sent in an e-mail message e. PKZIP password protected file that's been UUENCODED. If you wish to receive your key file by e-mail, you must make sure to send us your PGP public key. We will not send an unencrypted key file through the internet. With the exception of the diskette option, the file you'll receive will a self-extracting PKZIP compressed file. Option #2 --------- 2. All software sent on a diskette. Getting Updates --------------- Updates (which is the shareware version) can be downloaded from the following web sites (see below). As long as you have a valid, legal FWIN.KEY file, you can download the "shareware" versions from these sites to upgrade your copy of F/WIN. The FWIN.EXE file by itself is the "shareware" version. When FWIN.EXE and FWIN.KEY are used together, collectively they make up the fully-functional "registered" version. Here's how this works. When you run F/WIN Anti-Virus, the FWIN.EXE program looks to see if a valid FWIN.KEY file exists where it expects it to be. If FWIN.KEY is missing, FWIN.EXE is programmed to avoid activating some features. If a valid FWIN.KEY is found, then FWIN.EXE will activate all of its features. So you can keep downloading updated shareware versions, and have the most up-to-date registered version as well because of your FWIN.KEY file. See the price list in the ordering files for what it costs to receive update diskettes by mail 4 times a year. We also have an auto-responder set up that will allow you to send an e-mail message (with nothing in the subject or message; a completely blank message) to our WWW site, and have it automatically send you back through e-mail a UUENCODE'd version of the latest shareware release. This will allow anyone with internet e-mail access to get their updates (and the original shareware version) by e-mail, so long as they have UUDECODE software to decode it. To get the latest version of F/WIN Anti-Virus by e-mail, send a message (with nothing in the Subject line or body of the message) to: EVALUATE@FWIN.GEN.COM If you don't currently have UUDECODE, it is available at many FTP sites on the Internet. Our web page also contains the DOS and Windows version of UUENCODE/UUDECODE for you to download. Here's how to get to our web page: HTTP://WWW.GEN.COM/FWIN The shareware version may also be downloaded from: http://www.valleynet.com/~joe F/WIN may also be downloaded from any of the various SimTel FTP sites around the world. 3.4 In other countries For ordering the German version, contact Stefan Kurtzhals for purchasing instructions. All others please contact Gary Martin. Both can be contacted by e-mail through our web page specified above. 4.0 WINDOWS EXE VIRUSES ================================================================= 4.1. For NON-Technical readers ----------------------------------------------------------------- Until recently, {windows viruses} were very rare and primitive. In most cases they just converted the Windows executable format {NE-EXE} into normal {DOS-EXE} or used {companion style infection} and didn't change the programs at all. Furthermore, they all were {non-resident} {direct action} infectors which never spread very far. Viruses like {WinVir14} were to clumsy to escape into the {wild} and remained pure research viruses. But the situation changed after an underground virus magazine published the source code for a virus called {Winsurfer}. <Winsurfer> used a new {infection scheme} for infecting NE-EXE files. It was the first virus which was able to infect NE-EXE in a proper way without converting the program in DOS-EXE or by just creating companions. The new infection scheme is much less noticeable than the previous ones because it only changes a very small part of the {program header} and leaves the program still executable. Also, <Winsurfer> (and especially <Ph33r>) stay {resident} using the {DPMI API}. This gives them a much higher infection rate than the older direct action viruses. (<Ph33r> is a partial {fast infector}) Because this infection scheme is so clearly superior and additionally being published widely, it's very likely that more viruses will appear which copy this special method of infecting files. Windows 95 programs (32 bit EXE) have a new format, PE-EXE. The viruses that use the NE-EXE infection scheme don't infect this format, but as there are still some NE-EXE (16 bit EXE) left in Windows 95 or the user still uses old Windows programs, the viruses will still spread under Windows 95. Also, <Ph33r> infects DOS programs such as COMMAND.COM or WIN.COM beside infecting Windows EXE. The same underground virus writer group which created <Winsurfer> and <Ph33r> also managed to write a PE-EXE virus for Windows 95 executables. This virus is still quite clumsy (it's again just a direct action virus), but surely there will soon follow more complex viruses as the virus source was again published by the authors. 4.1.1 F/WIN's detection of Windows EXE viruses ----------------------------------------------------------------- F/WIN detects Windows EXE viruses by analyzing the NE-EXE and PE-EXE header of a file. The known Windows EXE viruses modify this header to an very unusual structure which can be detected by F/WIN. F/WIN does not check the program code which seems suspicious, and it will detect normal or variable encrypted {polymorphic} viruses because of this. 4.2. For Technical readers ----------------------------------------------------------------- Until recently, windows viruses were very rare and primitive. In most cases they just converted the Windows executable format NE-EXE into normal DOS-EXE or use companion style infection and didn't change the programs at all. Furthermore, they all were non-resident direct action infectors which never spread very far. Viruses like WinVir14 were to clumsy to escape into the wild and remained pure research viruses. But the situation changed after an underground virus magazine published the source code for a virus called <Winsurfer>. <Winsurfer> used a new infection scheme for infecting NE-EXE files. It was the first virus which was able to infect NE-EXE in a proper way without converting the program in DOS-EXE or by just creating companions. The new infection scheme is much less noticeable than the previous ones because it only changes a very small part of the program header and leaves the program still executable. In detail, the virus moves the NE header 8 bytes in order to get a free slot for a new segment entry which now points to the virus code. The virus code will then be added to the end of the file, storing the original entry point in a relocator entry behind the virus code. Also, <Winsurfer> (and especially <Ph33r>) stay resident using the DPMI API. This gives them a much higher infection rate than the older direct action viruses. (<Ph33r> is a partial fast infector) Because this infection scheme is so clearly superior and additionally being published widely it's very likely that more viruses will appear which copy this special method of infecting files. Windows 95 programs (32 bit EXE) have a new format, PE-EXE. The viruses that use the NE-EXE infection scheme don't infect this format, but as there are still some NE-EXE (16 bit EXE) left in Windows 95 or the user still uses old Windows programs, the viruses will still spread under Windows 95. Also, <Ph33r> infects DOS programs such as COMMAND.COM or WIN.COM beside infecting Windows EXE. The same underground virus writer group which created <Winsurfer> and <Ph33r> now also managed to write a PE-EXE virus for Windows 95 executables. This virus is still quite clumsy (it's again just a direct action virus), but surely there will soon follow more complex viruses as the virus source was again published by the authors. Actually, the virus is written for operating systems which support the Win32 API. At the moment, Win32 is supported by Windows (Win32s), Windows 95 and Windows NT. <PE.Boza> increases the amount of segments, changes the IP RVA to the new virus entry point, adds a new segment to the segment list (the new segment is named .vlad) and add the virus code at the end of the file. 4.1.1 F/WIN's detection of Windows EXE viruses ----------------------------------------------------------------- F/WIN detects Windows EXE viruses by analyzing the NE-EXE and PE-EXE header of a file. The known Windows EXE viruses modify this header to an very unusual structure which can be detected by F/WIN. Usually, they add strange segments which have no valid code segment flags set. F/WIN does not scan into these suspicious code segments, because there are yet too few Windows EXE viruses to derive a good code heuristic from them. Because F/WIN doesn't check the code of the virus, it is able to detect any unencrypted or polymorphic virus which use the <Winsurfer> or <Boza> infection schemes. 5.0 MACRO VIRUSES ================================================================= 5.1 What they are ----------------------------------------------------------------- Macro viruses which infects documents are fairly new. In the case of Microsoft Word templates, they use the built-in macro language called WordBasic. Other products like Excel, Word Perfect, etc. have their own built-in macro languages similar in function to WordBasic. Winword Macro viruses copy themselves into the global macro template and convert user documents into macro templates when the document is saved and infected. Also, the viruses use auto macros that are executed by WinWord automatically when for example a file is opened, saved or closed. Microsoft Word also allows execute-only macros which means that the user can't read the macro definition anymore, a feature which is used by most of the macro viruses. 5.2 History of ----------------------------------------------------------------- The idea of macro viruses by itself isn't new at all. In 1994 an example macro virus (<Winword.DMV>) was done to show the dangers of macro languages. This virus is a pure demonstration virus and was never spread. The first macro virus that escaped into the wild was <Winword.Concept>, which was released in 1995. Shortly after <Concept> other macro viruses where done, such as <Nuclear> and <Colors>. For more information about the known macro viruses to-date, use your web browser to link to: http://www.bocklabs.wisc.edu/~janda/macro_faq.html 5.3 Why they pose such a great threat to your data ----------------------------------------------------------------- There are two major reasons why macro viruses in general pose such a great potential threat to your data. First, macro languages like WordBasic (the macro language of Microsoft Word) are easy to learn. What keeps most people with bad intentions from writing DOS viruses is that DOS viruses are usually written in Assembler which is quite difficult to learn. But macro languages like WordBasic are significantly easier to learn and write viruses with than Assembler is. Coding examples for writing macro viruses can be found on the Internet. If your business uses one of the Microsoft Word templates that have been designed to intercept and remove viruses, then you have provided an excellent coding example to your employees for coding a WordBasic virus. Parts of those templates can be easily copied and modified to become destructive virus code. And the help screens that are available for WordBasic are plentiful. It would probably take the average programmer less than 10 hours to start with one of these anti-virus templates, and make a fully functional virus with highly destructive capabilities from it. The potential for data loss from a disgruntled employee is high if someone made a decision to attack your company in this manner. The second reason the risk is so high is that most virus scanners to-date only check for known macro viruses. They are not capable of detecting unknown ones, or if they do, they can misidentify what they've found. So if someone did plant a new virus that they just wrote in your business, you may not find it until it's too late. And it is very easy to create a 'new' undetectable virus by just inserting spaces and carriage returns into the macro code of a known virus. F/WIN's strength is that it finds both known and UNKNOWN WordBasic viruses and trojan's. F/WIN uses heuristic analysis instead of signature scans to find the viruses. F/WIN can also REMOVE most viruses it finds. And if it would happen to remove a virus in such a way where the document is no longer accessible, it makes a backup copy of the file before attempting to remove the virus. So F/WIN is both effective, and safe. Keep in mind that WordBasic is a powerful language. Beside the possibility of modifying almost every parameter and option of Winword, you can easily rename, change or delete other files (like WIN.INI, SYSTEM.INI, CONFIG.SYS etc.) and you can call other Windows or DOS programs, i.e. FORMAT or DELTREE. It's also possible to execute Win API calls or other embedded OLE objects. 5.4 F/WIN's detection of WordBasic macro viruses/trojans ----------------------------------------------------------------- When F/WIN analyses a document, it scans the whole file. This is necessary because of the complex internal format of document files (which are OLE objects). F/WIN tries to locate macro definition and macro list areas and then scans the target areas for suspicious commands or texts. Execute-only macros will get decrypted in memory while checked (it uses a technique similar to the 'x-ray' scanning method). F/WIN will analyze all the WordBasic tokens for virus like commands as FileSaveAs, CopyMacro and others. The macro name lists will be scanned for the presence of auto and system macros like AutoOpen or FileExit. After the end of the scanning process, F/WIN analyses the temporary results and tries to figure out if the macros are normal, or if they could represent a trojan or even a macro virus. Because of the complexity of OLE objects, F/WIN might fail to properly locate all macro areas in a file. This is not a real problem for virus detection, but it may cause problems while trying to clean the document. If the complete repair method fails (option 'C'), try the safer macro name wiping method (option 'W') which will work in almost every case. 5.5 How the viruses are removed ----------------------------------------------------------------- At this time, F/WIN only can remove macros from documents. It's not able to remove Windows EXE viruses. F/WIN offers two possible ways for removing macros. The Clean option (choose 'C') ----------------------------- For a Winword macro virus to work, two things must be present inside the Word template that's infected. First, there must be a macro name list area. It's similar to a Table of Contents in a book that point the reader to the page numbers of each chapter. It's how Word determines which macro's are present and where exactly they are placed. Then there's the macro definitions area. This is where the macro code itself is stored. The "Clean" function erases both areas. In our testing, the "Clean" function safely removed the viruses and trojans in the overwhelming majority of the cases. But there were some occasional incidents when the clean left the document unreadable. If this happens, just restore the document from the backup that F/WIN made and use the "Wipe" option to remove the virus instead. If the full cleaning method fails, F/WIN will produce the error message ('F/WIN can not clean this file safely!'). You should then try the macro name wiping instead. The Wipe option (choose 'W') ---------------------------- Because of the complexity of the internal template structures, the Clean option may fail. You can avoid this problem most of the time by using the Wipe option instead (option 'W'). "Wipe" overwrites (wipes) only the macro name list. It does not overwrite the virus code itself (the macro "definitions"). The virus/trojan code is only accessible with a disk editor after this kind of disinfection. But even a disk editor is quite useless in almost every case because the macros are usually encrypted and most people could not even find them, let alone decrypt and reuse them. There currently are no tools available to decrypt them, at least not ones available to the general public. It is quite unlikely that most people could do this, even skilled PC programmers. Once the macro definitions list has been erased, it is VIRTUALLY IMPOSSIBLE FOR WORD TO EVER FIND THE VIRUS CODE AGAIN. Your documents will be safe to use again. We have on very rare occasions, experienced situations in which even Wipe could not safely disinfect a template. In most of those cases, F/WIN clearly tells you that it could not safely remove the virus/trojan. You may then send it to your regular anti-virus company, or to F/WIN Support to have it removed. When comparing F/WIN with other macro anti-virus products, keep in mind than some virus scanners still don't include any kind of a cleaning facility at all or just clean the macro name list. REGARDLESS OF WHETHER YOU CHOOSE "CLEAN" OR "WIPE" F/WIN WILL REMOVE -ALL- MACROS FROM A DOCUMENT, NOT JUST THE ONES WHICH SEEMS TO CONTAIN SUSPICIOUS CODE. SO IF YOU DISINFECT YOUR NORMAL.DOT AND HAVE USEFUL MACROS INSTALLED, THEY WILL BE REMOVED TOO. Before starting the actual cleaning process, F/WIN will try to backup the target file by creating a copy of the file with ".Vnn" file extension. The file will not get modified if F/WIN fails to create a backup! Here's an example of how this naming scheme works. Assuming that you have eleven Word documents containing payroll information, and all are infected, here's how F/WIN would name the backup copies. Infected file Backup file ------------- ----------- PAYROLL.WK1 PAYROLL.VIR PAYROLL.WK2 PAYROLL.VI1 PAYROLL.WK3 PAYROLL.VI2 PAYROLL.WK4 PAYROLL.VI3 PAYROLL.WK5 PAYROLL.VI4 PAYROLL.WK6 PAYROLL.VI5 PAYROLL.WK7 PAYROLL.VI6 PAYROLL.WK8 PAYROLL.VI7 PAYROLL.WK9 PAYROLL.VI8 PAYROLL.WK10 PAYROLL.VI9 PAYROLL.WK11 PAYROLL.V10 (notice that the 'I' is now replaced by a '1') 6.0 F/WIN MESSAGES FOR WINDOWS VIRUSES ================================================================= 6.1 Possible 16-bit virus (NE-EXE) ----------------------------------------------------------------- F/WIN will display this message when it finds a Windows executable with a suspicious internal file structure. This will most likely indicate a Windows 3.x EXE virus infection. Please send such files to the F/WIN Support for analysis! It would be easy to ignore this message because of the use of the word "possible". We encourage you to take this message very seriously if you see it. We have had no instances in our testing where it has produced a false alarm but still the NE-EXE and PE-EXE heuristic analysis is quite 'weak'. 6.2 Possible 32-bit virus (PE-EXE) ----------------------------------------------------------------- Like NE-EXE viruses, F/WIN will detect this virus type by analyzing the internal file structures. At the moment, only one PE-EXE virus is known, <PE.Boza>. If you encounter a possible 32-bit virus infected file, please send us a sample for analysis! It would be easy to ignore this message because of the use of the word "possible". We encourage you to take this message very seriously if you see it. We have had no instances in our testing where it has produced a false alarm using the latest release of F/WIN. 7.0 F/WIN MESSAGES FOR MACRO VIRUSES ================================================================= 7.1 "A backup has been created" Before F/WIN removes a virus or trojan from a Word template, it first tries to make a backup copy of it. The backup copy will be unaltered, and will still contain the virus. F/WIN does this for two reasons. First, if the file is highly fragmented F/WIN may not be able to clean it properly. Since a backup is available, you can try a different approach. For instance, if the Clean function leaves it damaged, try the Wipe function instead on the backup copy. The second reason a backup is made is to allow recovery of macros that F/WIN flagged as dangerous, but that weren't. For instance, if someone wrote a macro to automatically delete all the *.TMP files that Word creates every time Word is opened, they would most likely us a 'Kill' command to do it. Since F/WIN would find this 'Kill' command, and see that it executes automatically, it would consider such a macro to be dangerous and it would remove it during the cleaning process. Having a backup copy allows the person using that macro to have it restored from a backup copy. This message tells the user that F/WIN was successfully able to make the backup copy. 7.2 "Attempt to backup file before cleaning failed!!" Before F/WIN removes a virus or trojan from a Word template, it first tries to make a backup copy of it. The backup copy will be unaltered, and will still contain the virus. See description of the "A backup has been created" message above for more information about why the backup is done. This message means that F/WIN could NOT create the backup file. F/WIN will NOT remove the virus from the original infected file if it can't successfully make a backup copy. There are a few possible causes. - the disk drive is out of space - the original file was damaged before F/WIN scanned it. An example of this would be a cross-linked file. A cross-linked file is a file whose disk space is partially shared by another file. When F/WIN can't clean it, it reacts one of two ways. If the /MOVE= parameter was specified, it literally moves the infected document to whatever directory was specified by the user in the /MOVE= command, except that F/WIN creates a directory below that one to actually place the file in. The sub-directory F/WIN creates for such instances is \BACKUP. So if /MOVE=C:\FWINBKUP was specified, F/WIN would actually move the file to C:\FWINBKUP\BACKUP\filename. Also, F/WIN renames the file extension. The old and new file names appear in F/WIN's report to make the file easy to locate after the scan is finished. If /MOVE= was NOT used, then F/WIN just leaves the file where it currently is, but still renames it. 7.3 "Changes DOS attributes of other files" The "attributes" of a file can be modified to change the way DOS views and stores a file. While there are legitimate reasons for changing the attributes of a file, viruses often remove the attributes before modifying files. READ-ONLY file attributes prevent a program from modifying a file while this attribute is enabled. SYSTEM or HIDDEN attributes are used by DOS and Windows to hide it's critical system files. Files with these attributes don't get listed with DIR or in the Explorer unless you configure them to do so. Some of the known macro viruses remove the system attributes of the IO.SYS and MSDOS.SYS files and then delete them. A regular macro does not contain such commands. This would probably be a good place to point out that the READ-ONLY attributes are no protection against viruses. These attributes can be removed and set without any problems by a virus. In fact, some resident file viruses (DOS) infect on setting the file attributes. 7.4 "Contains # macros (# bytes)" The '#' is replaced by an actual number in the message F/WIN produces. As a diagnostic aid, F/WIN will report how many macros it found, and the total number of bytes they utilize collectively. This can be helpful in determining if a new macro virus or trojan has been found. Here are the numbers that F/WIN produces for some common viruses and trojans: Winword.Trojan.FormatC - Contains 1 macro (81 bytes) Winword.KillDLL - Contains 1 macro (284 bytes) Winword.Wazzu - Contains 1 macro (644 bytes) Winword.Date - Contains 1 macro (1042 bytes) Winword.Guess - Contains 1 macro (1126 bytes) Winword.Devina - Contains 1 macro (2357 bytes) Winword.Imposter - Contains 2 macros (907 bytes) Winword.Doggie - Contains 3 macros (610 bytes) Winword.Atom - Contains 4 macros (1029 bytes) Winword.Concept - Contains 4 macros (1968 bytes) Winword.Boom - Contains 4 macros (2863 bytes) Winword.Hot - Contains 4 macros (5515 bytes) Winword.Colors - Contains 9 macros (6470 bytes) Winword.Nuclear - Contains 9 macros (10556 bytes) Winword.Xenios - Contains 11 macros (31342 bytes) If the infected Word template contained macros in it before it was infected, then some of those original harmless macros could still be present. In that case, the counts above would not match the counts you'd normally see for each particular virus. For instance, if a template contained 2 macros totaling 1000 bytes before being infected with the Concept virus, F/WIN's count would include those original macros plus those that were copied into the file by the Concept virus. So in this example, F/WIN might produce the following line for Concept: - Contains 6 macros (2968 bytes) 7.5 "Contains macro shortcuts" Normally, macro viruses must hook certain critical macros to get activated when you open an infected document. For instance, they create an "AUTOOPEN" macro to perform some function when the user "opens" a file. A lot of antivirus programs now intercept or detect these types of macros, but there's another method that is more difficult to detect. Instead of using system macros like AutoOpen or FileClose, macro viruses can assign shortcuts to macros. For example, you can assign a macro to the 'PgDn' (page down) key. Each time you press the key, the macro will get executed. So far, no virus is know to use this method, but this it will be just a matter of time before they do. And when they do, F/WIN will detect the key assignment and will allow the user to clean both the macro and the shortcut. 7.6 "Contains macros but is named .DOC" Templates which normally contain macros are usually named ".DOT". Winword, however doesn't need this special file extension to recognize macro templates. Macro viruses use this and keep the old ".DOC" extension after infecting a document, even if it's now a template rather than a document. By concealing the true file extension, the virus attempts to hide it's presence in infected files. Regular macro templates are named ".DOT", so if you find macros in a ".DOC" file it's quite suspicious, especially if they are auto macros or execute-only macros. 7.7 "Contains execute-only macros (encrypted macros)" There are two ways of storing macros in Word templates. The non-encrypting method allows Word users to look inside the macro just as they do a document and see what is coded in it. If the macro is a malicious one, someone who understands WordBasic can read the code and determine what it is trying to do. WordBasic is a programming language within Microsoft Word that allows Word users to create time-saving macros. Non-encrypted macros can also be modified into useful code, or into destructive virus or trojan code. The second way of storing a macro is to use the "execute-only" option. This option encrypts the macro so that it is no longer eye-readable. It also prevents the macro from being modified. However, it may still be renamed or deleted and of course, executed. Once a macro is encrypted, WordBasic provides no mechanism for decrypting it back into readable form. This is the choice method of storing macros for virus writers because most Word users will not be able to look inside suspicious macros to see what they're doing. Except for the information F/WIN can provide on such macros, in most cases, the document or template must be sent to an anti-virus company for analysis to get the full details on what it's trying to do. This message indicates that F/WIN has found at least one execute-only (encrypting) macro. However, F/WIN only displays this message if it finds potentially dangerous commands within the encrypted macro (F/WIN is able to look inside for you). If it simply finds an encrypted macro that has no dangerous WordBasic commands in it, this message will not appear. Execute-only macros are quite suspicious, but there are also commercial or shareware macros which uses the encryption to prevent modification of their code. 7.8 "Contains macros" This warning message indicates that macros are present in the template. However, this message will not appear unless potentially dangerous WordBasic commands are present in one or more of the macros. 7.9 "Copy macros into the global template ('CopyMacro')" This warning message indicates that the WordBasic "CopyMacro" command has been found in a macro. Of all the error messages that F/WIN produces, this one is probably the best at indicating the presence of a virus. Almost all Word viruses to-date have used the "CopyMacro" command to spread themselves from one Word template to the next. If products like SCANPROT.DOT are being used for anti-virus defenses, then there may be no cause for concern if this warning message is produced for a file called SCANPROT.DOT. SCANPROT.DOT is a Microsoft Word template developed by the Microsoft Corp. to help combat Microsoft Word viruses. SCANPROT.DOT contains several macros that use some of the same commands used by viruses. If SCANPROT.DOT is present, F/WIN will produce numerous warning messages when it analyzes it. See section "1.7 False alarms" in the F/WIN documentation to determine how to distinguish SCANPROT.DOT warnings from other ones. We want to make it clear that we are not suggesting that Microsoft is writing macro viruses. The SCANPROT.DOT file is a template that is intended to protect you against WordBasic macro viruses. Our point here is that it uses exactly the same WordBasic commands that some viruses use, so F/WIN will trigger warnings on SCANPROT.DOT when it scans it. There are other anti-virus templates besides SCANPROT.DOT that will trigger warning messages from F/WIN. If any such templates are scanned by F/WIN, in most cases, F/WIN will point this out by also producing a message that says, "Might contain an antivirus-macro (please verify!)". See 7.14 below for more information about that message. If you are sure that tools like SCANPROT.DOT are not in use, and that legitimate macros that used the CopyMacro function are not supposed to be in your environment, then it is quite likely F/WIN has detected an actual virus if this particular message is produced. Take this message very seriously, and have an expert investigate the documents in question. It is important to know if macros should be or should not be present in your environment so that you can distinguish real viruses from false alarms. Since most individuals and corporate users of Microsoft Word rarely if ever use macros, more often than not, this warning message will indicate the presence of an actual virus, or of an anti-virus template like SCANPROT.DOT. Macro viruses often use 'CopyMacro' together with auto macros like 'AutoOpen', 'AutoExec' or 'AutoClose' and are also often encrypted (execute-only macros). To hide themselves, they also often are not named ".DOT" but ".DOC instead. 7.10 "Deletes other files! (Kill)" This message indicates that the WordBasic "Kill" command is being used within a macro. The Kill command deletes files. You need to ask yourself, "why is my Word document deleting files?" This is not a common activity for a macro, and may indicate the presence of destructive code (macro trojan or virus). 7.11 "Disables NORMAL.DOT write access warnings" Most viruses will install their own special macros into the Global Template (the NORMAL.DOT file). This allows the virus to spread itself to virtually any template that is opened by the user. Microsoft Word has an option users can activate that alerts users to the fact that NORMAL.DOT has been changed. It's a pop-up window that asks if you want to save the changes to NORMAL.DOT. Some viruses disable this warning message through a certain WordBasic command, preventing the user from being warned that the Global template has been changed. This message is telling you that the warning message will be disabled if the macros in the file are allowed to run. 7.12 "Enables the quick save option" The Quick Save option allows users to speed up the process of writing to disk, the changes that have been made to a document. When the quick save option is on, only the changes that were made are saved. When it's off, the entire document is written back to disk during a save. While the quick save option has the benefit of makings saves run faster, it also makes virus detection and especially removal more difficult. The reason is because of what's known as "fragmentation". Fragmentation can be compared to a complex puzzle. When several saves have been done with quick save turned on, the file is stored similar to a puzzle with all the pieces mixed up. A language called "OLE2" (pronounced o-lay-two) manages all these pieces of data for Microsoft Word, and puts them all back together when a Word document is opened. But OLE2 is very complex. For a virus scanner to detect and remove viruses/trojans, it too must understand how to put all the pieces back together into the right order. Some virus authors are aware of the problems that the quick save option create for anti-virus products. As a result, they may turn the quick save option on in an attempt to make detection and removal more difficult. It's unusual for someone to code this option in a macro, so this may be an indication of an actual virus or trojan, especially if other strong indicators are present. Another reason virus authors might use the quick save option is because it speeds up the process of writing the virus to the template, thus making it a bit less noticeable to the user. 7.13 "Execute other DOS or Windows programs! (Shell)" This message indicates that another DOS or Windows program is being executed by a macro. This is quite suspicious. Why should a document execute a DOS or Windows program? While a legitimate, useful macro could do this, it's not common. Normally, macro viruses use this for dropping DOS viruses (like Winword.Nuclear does with Vlad.Ph33r) or they call FORMAT, DELETE, ERASE or other damaging DOS commands. 7.14 "F/WIN can not check Microsoft Word 2.0 documents!" At this time, F/WIN can not check for viruses and trojans in Microsoft Word 2.0 templates. However, this ability is coming in a later release. 7.15 "F/WIN can not clean this file safely!" The template is so internally fragmented that F/WIN has determined that it can not safely clean the virus or trojan using the CLEAN option (option 'C'). However, the user has the option of restoring this file from the backup copy that F/WIN made and trying to remove the virus with the 'W' option instead (W=Wipe Macro Names). The 'W' option should fail only on very rare occasions. 7.16 "has been moved to:" When F/WIN removes a virus/trojan from a Word file, it makes a backup copy of it first. This message tells the name of the original file, and of the backup file associated with it. For instance: DATE.DOC has been moved to: F:\FWINBKUP\BACKUP\DATE.VI0 This message says that "DATE.DOC" was the original file. If F/WIN was able to clean the virus/trojan successfully (it tells you when it can't), this file will be virus free. DATE.DOC is safe to open and use. The "DATE.VI0" file is the backup copy of "DATE.DOC" before the virus was removed. DATE.VI0 still contains the virus, so don't open it! If the cleaning failed, DATE.VI0 could be copied to another directory and a different cleaning approach could be used. 7.17 "Might contain an antivirus-macro (please verify!)" F/WIN has determined that the file MAY contain anti-virus macros which are intended to be helpful to the user, and that any warning messages associated with this file may be false alarms. See section 1.7 for more information about possible false alarms. In any case you should verify if this is really an antivirus macro. Some viruses could mask themselves as such useful macros. 7.18 "Might contain suspicious macros" This is reported when the macro contains suspicious operands and structures, but some parts are missing which are usually found in macro viruses or macro trojans. This will only be reported in the Extended or Paranoid scanning modes (/MODE=n or /PARANOID). 7.19 "Reenables auto macro processing" There are some macros that can be automatically executed if they exist in a template. They are AUTOOPEN, AUTOCLOSE, AUTOEXEC, and AUTONEW. AUTOOPEN, for instance, is executed automatically when a file is OPENed. Some users in an effort to protect themselves from macro viruses have disabled all four auto macros. This message indicates that code has been found that reactivate the auto macros. This function is common for viruses to allow them to spread more quickly and easily. 7.20 "Seems to be infected with a macro virus!" F/WIN detected enough suspicious structures which gives a very high chance that the reported document is infected with a macro virus (or is an anti-virus template like SCANPROT.DOT). Be aware, too that this message may also be produced for non-virus documents like SCANPROT.DOT, which are intended to protect you from macro viruses. These anti-virus macros contains almost the same WordBasic commands like a virus, so it's impossible to distinguish between them. 7.21 "Seems to contain a trojan macro!" This is reported if destructive commands are found and the WordBasic "CopyMacro" command isn't used. This can't be a virus, because it doesn't spread. A virus and a trojan can both contain destructive code. However, a virus spreads and a trojan does not. If you want to increase the trojan detection ability of F/WIN you could use the options /MODE=n or /PARANOID, but this also increase the chance of false positives! 7.22 "System macros:" A "system macro" is a macro that is executed automatically when the user performs a certain action. For instance, when a document is opened, the "AUTOOPEN" macro will be executed automatically if it exists (if automatic execution is enabled, which it is be default). If a file is saved, the FILESAVE macro will be executed if it exists. This messages indicates that F/WIN has detected the presence of one or more macros that will be automatically executed when some function is performed. The specific macros it finds are listed. The purpose/function of each one is briefly explained next. There could be a legitimate reason for the existence of these macros in your document. However, they may also be used by a virus or trojan, which usually contain "AutoOpen", "AutoClose" or "AutoExec". 7.22.1 AUTOCLOSE Called automatically if the user or Microsoft Word closes a document. 7.22.2 AUTOEXEC This macro is called automatically every time Microsoft Word is started (when you click on the Word icon). 7.22.3 AUTONEW This macro is called automatically every time a new document is created. 7.22.4 AUTOOPEN This macro is called automatically every time an existing document is opened. This is most often used by the macro viruses because it allows them to perform some activity (like spreading itself) right away if you try to read an infected document. 7.22.5 FILEEXIT This macro is executed when a file is closed (i.e. choosing "File", then "Close" from Microsoft Word). 7.22.6 FILENEW This macro is run when "File", then "New" are selected from Microsoft Word. 7.22.7 FILESAVE This macro is run whenever a file is saved. That includes when automatic, timed backups are made. 7.22.8 FILESAVEAS This saves a document to a different name and/or different file type. This macro must be redefined by macro viruses because they must convert documents into templates in order to save macros in the file. This macro will most likely only be included in the global macro template NORMAL.DOT. 7.22.9 TOOLSMACRO This function is called when the user tries to view, delete, rename or edit macros. Some of the macro viruses use this to infect further documents, or add some stealth functions which prevent the user from seeing the suspicious macros. DANGER!! Do not attempt to manually remove the virus or trojan by clicking on "Tools", then "Macro" when this message appears. The virus author may have coded some destructive code in the TOOLSMACRO macro that you will activate when you do this. Only allow an anti-virus program like F/WIN to remove the virus when you see that the TOOLSMACRO macro is present. 7.23 "The file has been moved to:" If F/WIN is unable to remove a virus from a file for some reason, or if it can't make a good backup copy of the file before removing it, F/WIN moves it from it's current directory to the one specified in the /MOVE= parameter, except that F/WIN creates a directory below that one to actually place the file in. The sub-directory F/WIN creates for such instances is \DAMAGE. So if /MOVE=C:\FWINBKUP was specified, F/WIN would actually move the file to C:\FWINBKUP\DAMAGE\filename. Also, F/WIN renames the file extension. The old and new file names appear in F/WIN's report to make the file easy to locate after the scan is finished. If /MOVE= was NOT used, then F/WIN just leaves the file where it currently is, but still renames it. This message tells the user that F/WIN successful in moving the infected file to the /MOVE= directory. 7.24 "The macros within this file are disabled!" Some antivirus programs clean macro virus in a special way. In order to avoid problems with complex (fragmented) documents, they just overwrite a few bytes in the macro list that tell Word that macros are present. Word checks this part of the document first to see if there are macros. If This particular area says there aren't any, then Word goes on about its business assuming that no macros are present, even thought they may actually be. This is a fast and easy way to disable the macros, and its effects are permanent. The macros can't be accessed anymore after this kind of cleaning. However, the macro code and names are still present in the file. A lot of antivirus programs can't handle such files correctly and still report them as infected. By default, F/WIN will ignore such 'corpses'. However, if the /MODE=2 or /PARANOID options were used, F/WIN will report these files and will display the message shown above. 7.25 "This document is internally fragmented. The repair could have failed !" The CLEAN option was chosen, but because of fragmentation in the file, the CLEAN may not have worked. It is suggested that you keep a copy of the backup files that F/WIN created until it can be confirmed that the document is still accessible. Better yet, rename the backup file and try to remove the virus with the 'W' option (Wipe Macro Names) option instead. In most cases, this will clean the file successfully. It might be helpful to explain in plain English what internal fragmentation is. A Word document/template can have many things stored within it. It can have tables, text, graphical images, macros, etc. All of these different components are stored like puzzle pieces that OLE2 can store in chronological order, or all mixed up. OLE2 is the file format that Word uses to manage the contents of Word documents and templates. How OLE2 is able to store these components all mixed up, and still present them all put back together for the user is a very complex process. Imagine if you had a 500 piece puzzle. Drop it on the floor, scramble it all around, then try to put it back together. That's somewhat similar to what an "internally fragmented" file is. Because OLE stored the document in such a scrambled manner, it knows how to put it all back together into something you can easily view when you open the file. Use of the Word QuickSave option is primarily responsible for causing this kind of fragmentation in Word documents. Because F/WIN is not a Windows program, it can't use the OLE API functions to read and analyze Microsoft Word documents. It has to figure out where the macros are stored in the document by itself and because of the complexity of OLE objects the cleaning may occasionally fail. If you get this warning you should try the 'Wipe macro names' option instead of the full cleaning. 7.26 "Uses macro 'FileSaveAs'" As said above, this is essential for macro viruses because they must convert documents into templates. In fact, if the user saves a file, the viruses internally uses FileSaveAs. In WordBasic, there is a FileSaveAs "macro name", and a FileSaveAs "WordBasic command". The macro internally calls the function, but the FileSaveAs macro could be redefined, i.e. to offer special prompts. 7.27 "Uses 'Organize .Copy' to copy macros" This warning message indicates that the WordBasic "Organize .Copy" command has been found in a macro. Like the "Copymacro" command (see 7.5 for details), this is a very strong indicator of the likely presence of a virus. Both perform the same function, they just do it in different ways. They copy a macro into another Word template. Most of the older macro viruses used CopyMacro to spread themselves. Recently, a new virus called "Boom" use the "Organize .Copy" command instead of "CopyMacro" to spread itself. Macro viruses often use 'CopyMacro' or 'Organize .Copy together with auto macros like 'AutoOpen', 'AutoExec' or 'AutoClose' and are also often encrypted (execute-only macros). To hide themselves, they also often are not named ".DOT" but ".DOC instead. Do not take this warning message lightly, especially if it appears along with several other strong warning messages. 7.28 "Writes into other files directly (Write)" This WordBasic command writes data directly into another file. Quite unusual for regular macros, but some macro viruses like <Winword.Xenixos> use this to drop DOS viruses into the system. They create a debug script file with the write command and then execute DEBUG to "compile" it. 8.0 COPYRIGHT, LICENSE TERMS AND DISCLAIMER ================================================================= See file "LICENSE.TXT". 9.0 GLOSSARY OF TERMS USED IN THIS DOCUMENTATION ================================================================= 16-bit EXE Windows 3.x uses a special executable file format, NE-EXE. Beside the old DOS EXE file header, it has a new NE header which specifies the locations and sizes of the code and data resources in the file. NE-EXE files still can call the DOS INT 21h or DPMI API functions. The first known virus for NE-EXE was <WinVir_1.4>. 32-bit EXE Windows 95 and Windows NT uses a new executable format, PE-EXE (Portable Executable). It is optimized for the 32-bit OS, i.e. by using 32-bit RVA's and supporting MMF (Memory Mapped Files). Like NE-EXE, they still have a normal DOS EXE header followed by the PE header which indicates the location and size of the file contents. PE-EXE run in flat protected mode and the program code can only call Windows API functions. The first known virus for PE-EXE was <Boza>. Auto Macro Auto macros are special Microsoft Word macros which are executed automatically by Word on certain events, i.e. like opening a document. To some degree, they can be disabled, but the macro viruses still have enough other ways to intrude the system. Boza <PE.Boza> is the first known virus for PE-EXE files (Windows 95), and comes from Australia. It's only a research viruses and not in the wild, mostly because it's just a direct action virus and has some bugs. COMMAND.COM The first normal DOS executable which is started at a system bootup. It only contains the command-line interpreter, but it's often a target for DOS file viruses. DOS itself is stored in MSDOS.SYS and IO.SYS (or IBMDOS.COM and IBMBIO.COM). COMMAND.COM itself executes AUTOEXEC.BAT. Companion Virus Companion Style Infection If you have two files with the same filename but different file extensions (one .COM, one .EXE) in the current directory and you execute the program without specifying an extension, DOS will always start the .COM program and not the .EXE. For example, if you have TEST.COM and TEST.EXE and execute "TEST", TEST.COM will be started. Companion viruses use this and creates corresponding .COM files to existing .EXE programs. These .COM files often have the HIDDEN attribute set in order to prevent detection (you will see this when you run tools like DEFRAG: the whole hard disk cluster layout is covered with single unmovable clusters). Concept The first Microsoft Word macro virus which appeared in the wild. It appeared in the mid of 1995 and spread rapidly world-wide. Beside displaying a window with a '1' in it, <Concept> is quite harmless. Together with some other macro viruses, <Concept> is now very common. Direct Action Infector A virus which actively scans the system for infection targets and doesn't go resident in memory. These viruses are not very viable and never spread very far because they are too obvious to the users and have a too low spread rate. All common viruses are resident. DOS-EXE The standard DOS executable format. It has a special EXE header, which is placed directly at the beginning of the file and is marked with a ASCII signature ('MZ'). The header will specify things like the program entry point, code size, amount of relocations, size of stack and others. Unlike .COM executables, EXE can be larger than 64K. DPMI API The DOS PROTECTED MODE INTERFACE API is used by real mode applications to interfere with the protected mode, i.e. mode-switching, transferring memory blocks, calling INT 21h from protected mode and other services. In real mode, the CPU only can access 1 MB of address space, in protected mode the memory is usually limited to 4 GB (real and virtual memory). Dropper File Sometimes viruses are hidden in a special dropper file. The virus is then often encrypted or compressed with special tools in order to prevent detection by virus scanners. Droppers are also used to 'install' boot viruses from files. <Winword.Nuclear> contains a debug script of the <Ph33r> virus, which will be dropped into the system sometimes. Encrypted Macro Execute-Only Macro Microsoft Word macros which can't be read or modified by the user anymore. It's only possible to execute, rename or delete such macros. Execute-only macros are often used by macro viruses to protect and hide their code. False Negative An infected file which is not detected by a virus scanner is called false negative. An uninfected file which is flagged as being infected by a virus is called false positive. Fast Infector At first, resident viruses only infected programs when the user execute the application by intercepting the INT 21h EXECUTE call. Newer file viruses also infect programs when they are opened or closed, which will cause very high spread rate for the virus. It is possible that a virus scanner will spread the virus infection, if the virus is a fast infector and unknown to the virus scanner. If you scan the hard disk with such a virus being active, almost every executable on the hard disk will get infected! Flat Protected Mode In flat protected mode, the memory is mapped as linear 4 GB address space. You don't need multiple selectors and can address the memory without much effort. Fragmented document (complex document) If you enable the FastSave option in Microsoft Word and change a document it will turn into a format that is called 'complex document'. The changes to the document will be stored at the end of the file, together with some links to the original positions. Also, the texts, graphics and macros in a document are treated as objects which can be split up and will get fragmented like a FAT hard disk. You even will get slack space areas like in FAT disk clusters. The FastSave option will also increase the size of the document compared to a normally saved document. In The Wild (ITW) Viruses, which have been found often and are very common are 'in the wild'. From the known 8500 viruses, only about 300 are in the wild. All other viruses are either extinct or research viruses, which never spread very far. Infection Scheme The way how a virus modifies an executable. Usually a virus changes the file header in way that it now points to the virus code, which is added at the file end. Some special viruses insert themselves at the file beginning or split up themselves throughout the file. Macro Microsoft Word macros contain WordBasic commands which can be used to speed up your work with Word. For example, you could write a macro which reformats a text block in a special way. Microsoft Word A word processor from Microsoft, which is used quite often. Word documents are OLE objects. NE Header The program header used by NE executables. Must be modified by Windows EXE viruses during the infection. NE-EXE See 16-bit EXE. Non-Resident See Direct Action Infector. NORMAL.DOT The global template of Microsoft Word. Beside some other things, global Word options and all global Word macros are stored in this file. NORMAL.DOT will be infected at once by most Winword macro viruses. PE header See 32-bit EXE. PE-EXE See 32-bit EXE. PGP PGP (Pretty Good Privacy) is a tool for encrypting data (i.e. e-mail) and verifying the integrity and source of data. It uses RSA and IDEA encryption and is very secure. Ph33r The second virus which used the <Winsurfer> infection scheme. Beside infecting NE-EXE, <Ph33r> also attacks DOS .COM and .EXE files and is memory resident using DPMI API calls. A <Ph33r> dropper was included in the <Winword.Nuclear> virus. Program Header Located at the beginning of executables, the program header specifies things like the program entry point, code size, stack size etc. File viruses must modify this part of the program during infection, but a lot of viruses are buggy and change the header incorrectly. Public Key Used by PGP. If you want to exchanged encrypted data with someone, you must exchange your public keys. Even if someone intercepted both public keys, he can't decrypt the transferred data because he doesn't have the private keys which are also protected with a password. Scan String Used by normal virus scanner to identify viruses. It's a byte signature which maybe contains wildcards and is like a 'fingerprint' to the virus, which will only detect this special virus. Virus scanners without heuristics will usually quickly be outdated because of the large number of new viruses which appear every day or month. Segment Because the normal CPU registers are 16 bit, you only can access 64K at a time. If you want to address other space you must change the segment registers. In the protected mode, you don't have this segment restriction. System Macro Beside auto macros, Microsoft word has other important macros like FileExit, ToolsMakros and others. This system macros are also often used and intercepted by macro viruses. Trojan A program which causes damage but unlike a virus it does not spread by itself. Unknown virus A (new) virus that is yet unknown to the virus scanners and is not detected by them without heuristics. Some of the heuristic scanners will detect about 60-90% of all new viruses. VBA (Visual Basic for Applications) The language used in the Microsoft Office products (Excel, Access) can also be used to write macro viruses. So far, there's only one know Excel virus (<Excel.DMV>), which is just a research virus. Virus A piece of executable code which is able to replicate and to insert a copy of itself into other executables. VLAD An Australian virus underground organization, which is responsible for a lot of very advanced viruses, like <Ph33r>, <Boza>, <MegaStealth> and others. Usually they release their latest viruses in an electronic magazine which is also called VLAD. WIN API The set of functions available to Windows programs. This contains functions like virtual memory management, file access, graphical operations and other things. There are a lot of different API's like Win32s, WinG and others. Windows EXE Can be either NE-EXE (Windows 3.x), PE-EXE (Windows 95 and Windows NT) or LE-EXE (used by some device drivers). See 16-bit and 32-bit EXE. Windows Virus A virus which is able to infect Windows executables or Windows related objects like Microsoft Word documents. Winsurfer A Windows NE-EXE virus which uses a powerful new infection scheme. WinVir14 The very first Windows virus, which never spread and is considered as a pure research virus, done by the virus coder group called Trident. Winword Word See Microsoft Word. WordBasic The macro language used by Microsoft Word. * F/WIN - Copyright (c) 1996 by Stefan Kurtzhals