Software Vault: The Gold Collection

home *** CD-ROM | disk | FTP | other *** search

/ Software Vault: The Gold Collection / Software Vault - The Gold Collection (American Databankers) (1993).ISO / cdr20 / pcl570.zip / VIRUS.TUT < prev next >

Wrap

Text File | 1993-06-10 | 25KB | 458 lines

---------------------------------------------------------------- VIRUS WARFARE: THE NOVEMBER MESSAGE ---------------------------------------------------------------- Interesting stories sometimes begin with a touch of horror. Technological terror is so much more invigorating when the plot is true and the author real . . . Imagine you are a computer operator at a local college on a crisp November afternoon. It is Monday and you have finished running a routine payroll data processing job which will print employee paychecks on Friday. You decide to check messages on the University computer network which links colleges and Universities throughout America. At 4:15 PM the following message flashes onto your screen. This message is NOT fictional. The dates and people are REAL: Monday, 30 November 1987 BITNET computer network - URGENT FROM: Kenneth R. Van Wyk, User Services Senior Consultant, Lehigh University Computing Center (215)-758-4988 <LUKEN@LEHIIBM1.BITNET> <LUKEN@VAX1.CC.LEHIGH.EDU> {RISKS-FORUM Digest Volume 5 : Issue 67} Last week, some of our student consultants discovered a virus program that's been spreading rapidly throughout Lehigh University. I thought I'd take a few minutes and warn as many of you as possible about this program since it has the chance of spreading much farther than just our University. We have no idea where the virus started, but some users have told me that other universities have recently had similar problems. The virus: the virus itself is contained in the stack space of COMMAND.COM. When a PC is booted from an infected disk, all a user need do to spread the virus is to access another disk via TYPE, COPY, DIR, etc. If the other disk contains COMMAND.COM, the virus code is copied to the other disk. Then, a counter is incremented on the parent. When this counter reaches a value of 4, any and every disk in the PC is erased thoroughly. The boot tracks are nulled, as are the FAT tables, etc. All Norton's horses couldn't put it back together again... :-) This affects both floppy and hard disks. Meanwhile, the four children that were created go on to tell four friends, and then they tell four friends, and so on, and so on. Detection: while this virus appears to be very well written, the author did leave behind a couple of footprints. First, the write date of the COMMAND.COM changes. Second, if there's a write protect tab on an uninfected disk, you will get a WRITE PROTECT ERROR... So, boot up from a suspected virus'd disk and access a write protected disk - if an error comes up, then you're sure. Note that the length of command.com does not get altered. I urge anyone who comes in contact with publicly accessible disks to periodically check their own disks. Also, exercise safe computing -always wear a write protect tab. :-) This is not a joke. A large percentage of our public site disks have been gonged by this virus in the last couple of days. END OF MESSAGE ... ---------------------------------------------------------------- COMPUTER VIRUSES: ELEGANT SOFTWARE WITH A SAVAGE PURPOSE ---------------------------------------------------------------- If you followed the previous message closely you are beginning to sense what a computer virus is and can do. A definition might roughly describe a VIRUS as a SELF-REPLICATING computer program which copies itself and attaches to one of the following areas of a computer: the hard disk partition table, the DOS boot sector of a hard disk or floppy or one or more executable files within the system. It may also make itself resident in RAM memory during computer operation. Infected executable files may be operating system programs, system device drivers, .COM files, .EXE files, overlay files or any other file which can be loaded into memory and executed. The virus activates itself at some predetermined (or randomly determined) time and attempts to destroy, remove or otherwise scramble data and programs. Some virus type even attempt to damage computer hardware. A trademark of a virus is that it is SELF-REPLICATING and thus clones multiple copies of itself. A virus is a computer program - designed by someone - to spread identical copies of itself among many computers and destroy data or programs in a specific targeted manner. In many ways a computer virus is quite similar to a biological virus. It attacks one computer then proliferates among many computers as infected floppy disks and the programs contained within are shared among many computer users. The virus may lie dormant for many months, or even years, all the while replicating its program code to many more programs and floppy disks. When an infected program is run it will in turn infect other programs and disks in that same computer. Sometimes, but not always, viruses interfere with printing or other routine DOS operations. Many times the programmer who designed the virus allows unintentional errors to exist within the virus program code which can cause unexplained system crashes and other odd behavior BEFORE the virus is triggered to erase or destroy data. It seems even viruses are not perfect programs and can be subject to programming bugs and errors just like standard programs! What does a virus program look like to a human operator? Simply a string of highly encoded computer data bytes which by themselves mean nothing to the casual observer. If you were to glimpse deep inside the computer program code which makes up a virus you might see something on your screen like the following "machine code" listing: xxxx:0110 02 00 02 3B A2 F8 29 00-11 00 04 00 11 00 80 00 xxxx:0120 00 00 00 00 0F 00 00 00-00 01 00 FA 33 C0 8E D0 xxxx:0130 BC 00 7C 16 07 BB 78 00-36 C5 37 1E 56 16 53 BF xxxx:0160 13 72 67 A0 10 7C 98 F7-26 16 7C 03 06 1C 7C 03 xxxx:0190 A1 34 7C E8 96 00 B8 01-02 E8 AA 00 72 19 8B FB xxxx:01B0 B9 0B 00 F3 A6 74 18 BE-5F 7D E8 61 00 32 E4 CD xxxx:01C0 16 5E 1F 8F 04 8F 44 02-CD 19 BE A8 7D EB EB A1 xxxx:01D0 1C 05 33 D2 F7 36 0B 7C-FE C0 A2 31 7C A1 2C 7C xxxx:0200 0C 01 06 2C 7C F7 26 0B-7C 03 D8 EB D9 8A 2E 15 xxxx:0210 7C 8A 16 1E 7C 8B 1E 32-7C EA 00 00 70 00 AC 0A xxxx:0230 18 7C FE C2 88 16 30 7C-33 D2 F7 36 1A 7C 88 16 xxxx:0240 1F 7C A3 2E 7C C3 B4 02-8B 16 2E 7C B1 06 D2 E6 xxxx:0250 0A 36 30 7C 8B CA 86 E9-8B 16 1E 7C CD 13 C3 0D Computer virus programs can be designed in assembly machine code, Basic, Pascal, C and even the DOS batch file language. What triggers a virus to destroy data once it is embedded within your computer? Depending on the person who designed the virus programming code, the virus can trigger and destroy data based on: A date, perhaps Friday the 13th to add a cruel twist of fate. The number of repetitions a certain program is run. An occurrence such as printing the payroll or running Lotus 123. A lack of an occurrence (removal of a name from a list.) A time of day, perhaps 1 AM when an office network is running unattended. A capacity, say when your hard drive reaches 90% capacity, nearly full. A random time of day or random date, or both. The presence of another program or removal of a program. Use of a modem or your printer. A particular person's name or password. Essentially, the programmer of the virus code selects a "trigger" of some type and deliberately programs the virus to wake up and "bite" when a certain condition is met! One of the original viruses designed to infect the IBM PC came from Pakistan where the programmers of the "Brain" virus wanted to punish American software users who copied or "pirated" commercial software. They did this by infecting illegal copies of commercial software which they sold in their retail store in Pakistan. In 1989 a large number of viruses were reported as originating in Israel. Some authorities speculate that PLO members might have written virus programs for political purposes to "punish" those living in Israel or America. Others speculate that those living in Israel might have designed the virus programs to penetrate complex computer networks in Arab countries or America to gain access to sensitive government data. Rumors continue to surface that perhaps the Russian KGB tried to develop a "super virus" that could penetrate NATO computer systems. In 1987, a European public BBS modem system was found to contain a highly specialized program "toolkit" designed by a young programmer. The purpose of this software toolkit was to assist in designing yet better and more clever virus programs! Private American BBS systems have been reported to exist wherein virus programmers trade virus program code examples and ideas on how to create "more savage" virus programs! These BBS systems have confidential telephone numbers and passwords so that only virus programmers can access these "virus libraries of information." What is the lure of programming a virus? The few programmers of virus software who have been caught usually explain their act as an intellectual challenge - an attempt to see how far programming code can be extended. In some respects this may be true. Virus programs are frequently crafted with obscure and highly elegant machine code and must be self replicating, self- modifying and "wired" with elaborate logic and algorithmic triggers. A virus must be small, fast and very stealthy. A virus in many respects is programming at the cutting edge of the craft, and perhaps this is the lure. ---------------------------------------------------------------- NOW THE BAD NEWS: VIRUSES AREN'T THE ONLY TOUGH KID ON THE BLOCK! ---------------------------------------------------------------- Perhaps we should back up and also define several other "rogue program" types which pose a security risk to your computer data. A TROJAN HORSE program appears as something useful - perhaps a program to sort names or print a list of telephone numbers on the computer. Yet it actually does something destructive either immediately or at a later time. As an example, several trojan horse programs offer to display X-rated images or colorful games which distract your attention to the screen long enough for the program to cheerfully erase your bookkeeping data. A trojan horse might (but does not usually) replicate its code to several other disks. This replication feature is more distinctive of a true virus. A LOGIC BOMB is much like a trojan horse and may lie hidden within a useful program. However when a certain point of logic or data is presented to the program (e.g., the programmer's name is removed from the company payroll records presumably because the programmer has been fired) then the logic bomb is activated to "extract revenge" by scrambling payroll records or perhaps removing all occurrences of the numbers 4, 7 and 9 from any data throughout company records. Insidious . . . A WORM is somewhat similar to a virus. It can replicate and spread throughout a computer system. When the worm program is run is creates copies of itself and runs those copies. It can wreak havoc on interconnected computer systems such as are found within university networks or government computers. A well-known worm infection occurred in the Fall off 1988 when a worm program was installed on a large internet network and quickly spread through hundreds of government and university UNIX type computers. All of the infected computers quickly bogged down as the worm created and then ran many copies of itself thus demanding more and more memory and computing time from legitimate programs and more necessary work tasks. A word before we continue. Virus programs are not THAT common. They are real, but have been vastly over-reported in the popular press. They seem to be more common within university communities where youthful students might be tempted to "test" their programming skills by creating virus programs. Commercial software has OCCASIONALLY been infected, but for practical purposes, commercial programs purchased from retail sources and packed in original factory boxes are low probability sources of viruses. Public domain and shareware sources of software as well as BBS/modem sources are sometimes suspected of virus infection, but most reputable shareware distributors and BBS systems report low computer virus incidence. Indeed, the shareware and public domain software community is more rigorous in routine testing for virus infections than the commercial software development houses. Computer virus programs DO exist, but they are quickly caught and erradicated from most BBS systems and shareware sources. Your chance of computer virus infection is probably on the order of 2% probability, but knowledge and foresight are a wise investment in computer and data security! Published lists of virus programs detail unique virus names and characteristics. One of the better virus lists is the shareware software program DIRTY DOZEN which is available from most computer clubs and many BBS systems. Some examples of virus programs which have been identified include: ICELANDIC PENTAGON DARK AVENGER SYSLOCK DISK KILLER/OGRE ZERO BUG VACSINA DATACRIME TRACEBACK What can you do to protect your computer data? Make frequent backups of data you consider essential. To "backup" means to routinely copy important files from your hard drive to floppies or other portable magnetic media. Weekly file backup is a minimum. Daily is not unreasonable. Consider rotating between two or three sets of backups (use backup floppy set #1, then set #2 then set #3 - then back to set #1 and so on). Limit the exchange of data disks within your workplace unless necessary - especially if those disks contain EXE or COM files. Always write protect all floppies unless they are data disks which must be updated routinely. If you find a file on a public BBS system interesting, leave it there for a month and wait to see if other users report problems with the program. This pessimistic outlook may save considerable hard disk data. Other common sense suggestions for preventing virus outbreaks include the following: Avoid sharing commercial software and making copies for others. It is a violation of the author's copyright to copy commercial software, in any event. Always obtain public domain and shareware software from reliable sources such as large BBS systems - Compuserve and PC MagNet are relatively reliable as are large shareware distributors such as PC SIG and Public Brand Software who obtain their copies directly from the author via US mail. If possible, use one of the many virus checking programs on the market to test public domain and shareware software prior to installation on your system. Test ALL of your system's files - perhaps at the same time as you perform routine backups - as a monthly or weekly routine. The first time you start a suspected public domain/shareware program run it from a floppy disk and not your hard drive. Always write protect your floppies if possible. Use one of the available "vaccination programs" which continuously monitor your system for unauthorized or otherwise unexpected data transfers. These programs monitor your hard disk and memory for activity not usually normal under DOS operations. If you do detect a virus program, consider that both your hard disk and your backup copies are probably infected. Keep original application disks from the manufacturer safely tucked away and protected by write protect tabs so they cannot be infected. Never start a hard disk-equipped computer from a floppy disk except the ORIGINAL DOS disk which is WRITE PROTECTED with a tab in place. No exceptions! Curiously, 90% of those infected with a virus or trojan horse program are reinfected within a month! This attests to widespread sharing of data disks and poor data work habits. Don't always assume a computer problem is virus related. Most of the time it is related to improper equipment use. Carefully scrutinize file directories on your disk(s) for date or file size changes. Viruses are fond of adding their code to the files COMMAND.COM, IBMBIO.COM, or IBMSYS.COM. Perhaps jot down or print out known file sizes and dates of creation and check for any changes which may appear since you first installed that file on your disk. Both commercial and shareware/public domain software programs exist whose purpose is to detect and repair damage caused by virus software: Software Program Purpose and method of action ------------------------------------------------------------------ Viruscan & From McAfee Associates telephone (408) 988-3832. Clean Available from most BBS's, computer clubs, this is an exceptional program, updated frequently. Scans drives and RAM memory for virus presence. The program is proactive: is searches for exact virus "flags" rather than waiting for a virus to hit. Program is self-testing to make sure that it has not itself been infected! The scan program searches for the virus, the clean program attempts to remove it. F-Prot From Fridrik Skulason, Reykjavik, Iceland. Available from most BBS systems and shareware vendors. Reliable and inexpensive virus utility. Has scored higher on some tests than McAfee's Virus Scan program. VIRX Runs faster than Viruscan and detects and deletes many of the same viruses. From Microcom, Inc. POB 51816, Durham, NC 27717. Dirty Dozen Detailed list of virus and trojan horse programs which is available from most computer clubs or shareware distributors. Interesting reading. Dr. Solomon's A commercial virus detection and removal Toolkit utility. Performs well. (800) 872-2599 AntiVirus From Central Point Software. Another highly regarded commercial virus detection and removal utility. (800) 445-2110 PC Magazine Checks and verifies your files and allows PCDATA continuous testing prior to virus infection. Free from computer clubs, shareware outlets, BBS's. See February 13, 1990 edition, PC Magazine. Cleverly provides backup for crucial data and makes unique "fingerprint" of sensitive files. DBack Backup FAT Tables, similar capability in PCDATA. PC-Tools Deluxe Repairs damage to file allocation table and damaged files Mace+ Repairs damage to file allocation table and Utilities damaged files Norton Utilities Repairs damage to file allocation table and damaged files ---------------------------------------------------------------- WHAT NEXT? - WHAT TO DO WHEN A VIRUS BITES ---------------------------------------------------------------- The cat is out of the bag and you are pretty sure - that sinking feeling - that a virus is in your computer. What next? If you don't want to try to unravel the mess yourself, try calling McAfee Associates at the telephone number listed above. They can send you a diagnosis program (VIRUSCAN) and virus removal program - also available from most computer clubs and shareware vendors. In the case of boot sector infestations, power down your system then restart from an uninfected write-protected ORIGINAL COPY DOS disk. Execute the DOS SYS command to attempt to overwrite the boot sector with new startup files. This will work in most cases. If it does not work, backup all data files which are essential (and maybe infected) then perform a low level format of the hard disk or a normal format if it is an infected floppy disk. Do likewise for ALL floppies which may have come into contact with the virus. When you are done, use VIRUSCAN to check for the presence of continuing virus infestation. If an EXE or COM file has been infected, power down the system, reboot from the factory WRITE PROTECTED DOS disk, delete all infected COM and EXE files then replace them with the original files from the WRITE PROTECTED, factory original program disks. Run any virus detection utility again to check for absence of the virus. For a disk partition table infection the only option short of a removal utility is to low level format the disk. And with that action destroy not only the virus but also your data. Better hope you have backup data on a floppy disk! After disinfecting a hard disk, you MUST test and probably reformat EVERY floppy that came into contact with the infected computer. If you are reinstalling a backup copy, do not restore it unless it was made BEFORE the system became infected. Run a virus testing utility to be sure. For additional help, consider contacting the National Computer Security Association at 717/258-1816 or McAfee Associates at 408/988-3832. Tutorial finished. Have you registered PC-Learn to receive your bonus disks? Registration is encouraged. Shareware works on the honor system! Send $25 to Seattle Scientific Photography, Department PCL5, PO Box 1506, Mercer Island, WA 98040. Latest version of PC-Learn and two bonus disks shipped promptly!