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1990-12-13
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VSHIELD Version 2.8V72
VSHIELD1 Version 0.1
Copyright (C) 1990 by McAfee Associates.
All rights reserved.
Documentation by Aryeh Goretsky.
McAfee Associates (408) 988-3832 office
4423 Cheeney Street (408) 970-9727 fax
Santa Clara, CA 95054-0253 (408) 988-4004 BBS 2400 bps
U.S.A (408) 988-5138 BBS HST 9600
(408) 988-5190 BBS v32 9600
TABLE OF CONTENTS
SYNOPSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
- What VSHIELD is, system requirements
AUTHENTICITY . . . . . . . . . . . . . . . . . . . . . . . . . .2
- Verifying the integrity of VSHIELD
WHAT'S NEW . . . . . . . . . . . . . . . . . . . . . . . . . . .3
- Features, new viruses added in this release
OVERVIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
- Detailed description of VSHIELD
OPERATION. . . . . . . . . . . . . . . . . . . . . . . . . . . .6
- Options to use with VSHIELD
EXAMPLES . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
- Samples of frequently-used options
INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . . .9
- How to install VSHIELD on your system
EXIT CODES . . . . . . . . . . . . . . . . . . . . . . . . . . .9
- For running VSHIELD from batch files
VIRUS REMOVAL. . . . . . . . . . . . . . . . . . . . . . . . . .10
- What to do if a virus is found
REGISTRATION . . . . . . . . . . . . . . . . . . . . . . . . . .11
- How to register VSHIELD in the U.S. and abroad
TECH SUPPORT . . . . . . . . . . . . . . . . . . . . . . . . . .11
- Information you should have ready when calling
VERSION NOTES. . . . . . . . . . . . . . . . . . . . . . . . . .12
- Program history
Page 1
VSHIELD Version 2.8V72 Page 2
SYNOPSIS
VSHIELD is a virus prevention program for IBM PC and
compatible computers. It will prevent viruses from infecting your
system. When VSHIELD first loads it will search the PC for known
computer viruses in memory, the partition table, boot sector,
system files, and itself and then install itself as a
Terminate-and-Stay-Resident (TSR) program. It will then scan all
programs before allowing the system to execute them. If any
program contains a virus, VSHIELD will refuse to allow it to
execute. It will also not allow the system to be warm-booted from
any diskette which contains a boot-sector virus. VSHIELD can
optionally check files that have been validation coded by the
VIRUSCAN (SCAN) program for new, unknown viruses.
VSHIELD can monitor a system for viruses by checking a program
for virus signatures, checking the validation code added by the
VIRUSCAN program to a file, or do both. Two separate programs are
available. The first, VSHIELD.EXE, does known-virus and validation
checking. The second program, VSHIELD1.EXE, does validation
checking only. The VSHIELD programs will monitor all program loads
regardless of the disk they occur on.
VSHIELD will run on any PC with 256Kb and DOS version
2.0 or greater. VSHIELD1 uses 6Kb of system memory. VSHIELD uses
36Kb of system memory, or 2.9Kb if swapping-to-disk is specified.
AUTHENTICITY
VSHIELD is packaged with the VALIDATE program to ensure the
integrity of the VSHIELD.EXE and VSHIELD1.EXE files. The
VALIDATE.DOC instructions tell how to use the VALIDATE program.
The VALIDATE program is distributed with VSHIELD and may be used
to check all future versions of VSHIELD.
The validation results for the VSHIELD Version 72 and VSHIELD1
Version 0.1 programs should be:
FILE NAME: VSHIELD.EXE VSHIELD1.EXE
SIZE: 27,811 10,753
DATE: 12-13-1990 10-04-1990
FILE AUTHENTICATION
Check Method 1: DA3E 689F
Check Method 2: 0A4B 0188
If your copy of the VSHIELD programs differ, they may have been
modified. Always obtain your copy of VSHIELD from a known source.
The latest version of VSHIELD and validation codes for VSHIELD.EXE
and VSHIELD1.EXE can be obtained off of McAfee Associates bulletin
board system at (408) 988-4004.
VSHIELD Version 2.8V72 Page 3
WHAT'S NEW
Version 72 prevents four new viruses, bringing the number of
known computer viruses to 162 known computer viruses, and their 261
associated variants:
The ZeroHunt virus was uploaded to Homebase BBS by Paul
Ferguson of Washington, D.C., USA. It is a memory-resident
infector that attaches itself to the stack space in .COM files.
Since the virus is attaching itself inside a file, as opposed to
adding itself to the beginning or end, the size of the file will
not change.
The Bloody! virus has been reported in Massachusetts, USA as
well as Taiwan and Europe. It infects the boot sector of a floppy
disk and the partition table of the hard disk. After approximately
128 reboots, the virus displays the message "Bloody! Jun. 4, 1989"
which is the date of the Tiananmen Square Massacre in Beijing,
China.
The Jeff virus is a .COM file infector that destroys data by
writing garbage to the hard disk. It contains the text "Jeff is
visiting your hard disk."
The Music Bug virus has been reported in Woodland Hills,
California and Orlando, Florida as well as Taiwan. It infects the
boot sector of a a floppy disk and the partition table of the hard
disk. The Music Bug plays child nursery tunes after a specified
time. It contains the text "MusicBug v1.06. MacroSoft Corp."
Beginning with Version 72, all McAfee Associates programs for
download are archived with PKWare's PKZIP Authentic File
Verification. If you do not see the "-AV" message after every file
is unzipped and receive the message "Authentic Files Verified!
# NWN405 Zip Source: McAFEE ASSOCIATES" when you unzip the files
then do not run them. If your version of PKUNZIP does not have
verification ability, then this message may not be displayed.
Please contact McAfee Associates if your .ZIP file has been
tampered with.
VSHIELD Version 3.8V72 Page 4
OVERVIEW
VSHIELD is a memory-resident program that prevents viruses
from infecting your computer. VSHIELD does this by checking
program files before they are loaded into the computer and
executed. If a virus is found and/or if the program no longer
matches it's validation check, VSHIELD will not allow the file to
be executed, preventing the virus from infecting your system.
VSHIELD will also check the disk the computer is booting from for
boot sector and partition table viruses. In the event that one is
found, VSHIELD will not allow the system to reboot, and instead
will prompt the user to insert a clean, write-protected boot disk
and run the VIRUSCAN program to remove the infection.
When VSHIELD is placed in the AUTOEXEC.BAT file, it will
install itself each time the system is turned on or rebooted. It
will proceed to check the memory, partition table, boot sector,
system files, and itself for viruses and then install itself as a
Terminate-and-Stay-Resident (TSR) program. It then monitors all
program loads for viruses. If a virus is found using Level I
protection, a warning message will be displayed stating the name
of the modified file. If a virus is found using Level II or III
protection, a warning message will be displayed stating the
filename and name of the virus. Loading will then be terminated,
preventing execution of the system by the infected program.
When the power is turned off and the system is booted off of
an infected floppy (without VSHIELD) VSHIELD will detect the
infection the next time VSHIELD is executed. VSHIELD level II and
III protection will also prevent partition table and boot sector
infector viruses from infecting the system during a reboot of the
system (Ctrl-Alt-Del) by examining the diskette being booted from
and halting the reboot process if a virus is found.
VSHIELD has three levels of user-selectable protection:
- Level I protection, provided by the VSHIELD1 program, checks
the Cyclic Redundancy Check (CRC) validation code values added
to programs by the VIRUSCAN program's /AV option. If a
program no longer matches its validation code VSHIELD1 will
not allow it to execute. VSHIELD1 will also check the
partition table and boot sector validation codes, if present.
Level I protection provides a minimal degree of protection,
and it is recommended that Level II protection or above be
used if system resources permit.
- Level II protection, provided by the VSHIELD program, checks
program files for virus signatures. A virus signature is a
piece of code or pattern unique to each computer virus strain.
VSHIELD will check the memory, partition table, boot sector,
system files, and itself for viruses before installing itself
as a TSR program. It will then check programs loaded after
it installs itself for computers viruses. If a virus is
found, VSHIELD will not allow the program to execute. VSHIELD
will also not allow a computer to be warm-rebooted from a
diskette infected with a partition table or boot sector
infector.
VSHIELD Version 2.8V72 Page 5
- Level III protection is a combination of Level I and Level II
Protections.
Each level of protection has its advantages and disadvantages.
The Level I protection requires the least amount of system
overhead, using 6Kb of system memory. It provides minimal
protection, however.
The Level II and III protection requires 34Kb of system
memory, but this can be reduced to 3Kb by using the /SWAP option.
The /SWAP option leaves a VSHIELD kernel in memory that swaps
the main body of the program in and out of memory as needed.
VSHIELD will add an average of three seconds to each program
load, and five seconds to each reboot. Using the /SWAP option will
add an additional 600 milliseconds to each program load. VSHIELD
will not degrade the performance of the system in any way once a
program has been loaded.
VSHIELD1 will add an average of 1 second to each program load.
NOTE: VSHIELD and VSHIELD1 should not be used simultaneously.
Either one or the other should be selected.
VSHIELD Version 2.8V72 Page 6
OPERATION
IMPORTANT NOTE: CREATE A BACKUP DISK BY COPYING THE VSHIELD
PROGRAMS TO A BLANK FLOPPY AND WRITE-PROTECTING IT BEFORE RUNNING
THE PROGRAMS. THIS WILL GIVE THE USER A VALID BACKUP IN CASE THE
PROGRAMS BECOME INFECTED.
VSHIELD and VSHIELD1 will monitor your system for attempts to
load an infected program. If an infected program is loaded,
VSHIELD will display a message stating the name of the file, the
virus infecting it, and will prevent the file from being executed;
and VSHIELD1 will display a message stating the name of the file,
the fact that it has been modified, and will prevent the file from
being executed.
To run VSHIELD type:
VSHIELD /CV /F pathname /LOCK /M /NB /NOMEM /SWAP pathname /X
Options are:
/CV - Check validation codes added by VIRUSCAN
/LOCK - Disable /REMOVE option
/NOMEM - Skip memory checking
/REMOVE - Uninstall VSHIELD from memory
/SWAP pathname - Install VSHIELD kernel as memory-resident
/F pathname - Required parameter for DOS 2.0 or earlier
/X - Check for extinct viruses
(removed for this version)
The /CV option checks validation codes inserted by the
VIRUSCAN program to provide Level III protection as defined above.
If a file no longer matches its validation code, VSHIELD will
report that the file has been modified, that viral infection may
have occurred, and will not allow the program to execute. If the
/CV option is not specified, VSHIELD will provide Level II (virus
signature) checking only.
The /F option is required if the user wishes to use the /SWAP
command and is running DOS 2.0 or earlier. The /F option tells
VSHIELD where it has been loaded from. The complete pathname must
be specified.
The /LOCK options will lock the system if a virus is found so
that processing cannot continue.
VSHIELD Version 2.8V72 Page 7
The /NOMEM option is used to turn off all memory checking for
viruses during installation. It should only be used when a system
is known to be free of viruses. This option can not be used with
the /M option.
The /REMOVE option will uninstall the VSHIELD program and
remove it from memory. If other memory-resident programs prevent
VSHIELD from being uninstalled an error message will appear.
The /SWAP option tells VSHIELD to install only its kernel as
memory resident. The VSHIELD program will then be swapped in and
out of memory as needed from a hard disk or RAM disk. The
placement of a path after the /SWAP command is optional, and should
only be used if VSHIELD is to be swapped from other than the path
from which it is being executed.
NOTE: The /SWAP parameter should only be used if the computer has
a limited amount of system memory available for memory-resident
programs. It is recommended that VSHIELD be used without the /SWAP
option whenever memory permits.
The /X option is used to check for extinct viruses. An
extinct virus is defined as a virus from which there have been no
infection reports in the preceding twelve (12) months, or a virus
that was created as a research tool and does not exist outside of
a few tightly-controlled copies.
VSHIELD Version 2.8V72 Page 8
To run VSHIELD1 type:
VSHIELD1 /NB
Options are:
/NB - Bypass boot sector checking
The /NB option will tell VSHIELD not to look at the partition
table and boot sector. This option should only be used if VSHIELD1
continually reports that the boot sector has been modified. This
occurs on some old Hewlett Packard and Zenith systems because they
modify the boot sector each time the system is booted. Check your
system's manual to determine if your system contains self-modifying
boot code.
NOTE: The VSHIELD1 program can not be uninstalled from memory.
The system must be rebooted to remove it.
EXAMPLES
The following examples are shown as they would be typed in on
the command line.
VSHIELD1
To install VSHIELD1 (Level I protection)
VSHIELD
To install VSHIELD (Level II protection)
VSHIELD /CV
To install VSHIELD (Level III protection)
VSHIELD /SWAP
To install VSHIELD kernel only as memory resident and
swap from root directory of disk on DOS 3.0+ system
VSHIELD /SWAP /F C:\VSHIELD.EXE
To install VSHIELD kernel only as memory resident and
swap from root directory of disk on DOS 2.0 system
VSHIELD /CV /M /X
To install VSHIELD using Level III protection, scanning
of memory for all memory-resident and extinct viruses
during installation, and monitor system for extinct
viruses.
NOTE: Do not run VSHIELD.EXE and VSHIELD1.EXE at the same time.
If you wish to switch programs, change the AUTOEXEC.BAT entry and
reboot the system.
For information about the installation of CRC validation codes,
please refer to the VIRUSCAN program's documentation.
VSHIELD Version 2.8V72 Page 9
INSTALLATION
VSHIELD and VSHIELD1 should be normally placed at the
end of the AUTOEXEC.BAT file. The exception is any AUTOEXEC file
that contains a DOS Shell routine. In this circumstance, VSHIELD
or VSHIELD1 should be loaded immediately prior to the Shell
routine.
If network drivers are being used, VSHIELD *MUST* be
loaded AFTER the network drivers, preferably at the end of the
AUTOEXEC. This is because network drivers replace normal DOS
functions in a manner that prevents VSHIELD from recognizing
program loads if VSHIELD is loaded first. Running VSHIELD after
network drivers have been loaded will ensure proper virus
protection.
It is recommended that VSHIELD be used in non-swap mode if
free memory permits. Use of the /SWAP option may cause conflicts
with programs that fail to allocate memory properly. If conflicts
occurs do occur, remove the /SWAP option and reboot the machine.
If there is not enough memory to load VSHIELD in non-swap mode,
than the VSHIELD1 program should be used instead.
ERROR LEVELS
VSHIELD will set the following DOS ERRORLEVELS prior to going
resident:
VALUE | DESCRIPTION
------+--------------------------
0 | No viruses found
1 | One or more viruses found
2 | Abnormal termination (program error)
If the user stops VSHIELD from installing, the ERRORLEVEL will be
set to 2.
VSHIELD Version 2.8V72 Page 10
VIRUS REMOVAL
What do you do if a virus is found? You can contact McAfee
Associates for assistance with manually removing the virus, for
disinfection utilities, and for more information about the virus.
When an infection is found, the VIRUSCAN program should be run
to scan the entire system to determine the extent of infection.
The VIRUSCAN program is available for download off of McAfee
Associates BBS.
The CLEAN-UP universal virus disinfection program is available
and will disinfect the majority of reported computer viruses. It
is updated frequently to remove new viruses. The CLEAN-UP program
can be downloaded from McAfee Associates BBS.
It is strongly recommended that you get experienced help in
dealing with viruses, especially critical viruses that can damage
or destroy data [for a listing of critical viruses, see the /M
option under OPTIONS, above] and partition table or boot sector
infecting viruses, as improper removal of these viruses could
result in the loss of all data and use of the disk(s).
BOOT SECTOR INFECTORS
Power down the infected system and boot off of an uninfected,
write-protected diskette. Use the DOS SYS command to attempt
to overwrite the boot sector. This works in many cases. Run
VIRUSCAN to see if the virus has been eradicated. If this
does not work, do a file-by-file backup of the system followed
by a low-level format of the disk. For a floppy diskette,
copy the files off of the infected diskette using the DOS COPY
command, not XCOPY or DISKCOPY which can transfer the virus.
Reformat or discard the infected floppy.
FILE INFECTORS
Power down the infected system and boot off of an uninfected,
write-protected diskette. Run VIRUSCAN with the /D and /A
options. Scan all original disks for viruses and replace
programs from them if clean.
PARTITION TABLE INFECTORS
Power down the infected system and boot off of an uninfected,
write-protected diskette. Proceed to a file-by-file backup
of the system (in other words, do not backup the partition
table) and do a low-level format of the disk.
Disinfection utilities are available for the majority of reported
computer viruses, these programs can be downloaded directly from
McAfee Associates' BBS or purchased directly from McAfee
Associates.
VSHIELD Version 2.8V72 Page 11
REGISTRATION
A registration fee of $25.00US is requested for the use of
VSHIELD by individual home users. Registration is for one year and
entitles the holder to unlimited free upgrades for the duration off
of McAfee Associates bulletin board. Diskettes are not mailed
unless specifically requested. Add $9.00US for diskette mailings.
Registration is for home users only and does not apply to
businesses, departments, organizations, government agencies, or
schools, who must obtain a license for use. Contact McAfee
Associates for more information.
Outside of North America, registration and support may be
obtained through the agents listed in the accompanying AGENTS.TXT
text file.
TECH SUPPORT
In order to facilitate speedy and accurate support, please
have the following information ready when you contact McAfee
Associates:
- Program name and version number.
- Type and brand of computer, hard disk, plus any
peripherals.
- Version of DOS you are running, plus any TSRs or device
drivers in use.
- The exact problem you are having. Please be specific as
possible. Having a print out of the screen and/or being
at your computer will help also.
McAfee Associates can be contacted by BBS or fax twenty-four hours
a day, or call our business office at (408) 988-3832, Monday
through Friday, 8:30AM to 6:00PM Pacific Standard Time.
McAfee Associates (408) 988-3832 office
4423 Cheeney Street (408) 970-9727 fax
Santa Clara, CA 95054-0253 (408) 988-4004 BBS
U.S.A (408) 988-5138 BBS HST 9600
(408) 988-5190 BBS v32 9600
VSHIELD Version 2.8V72 Page 12
VERSION NOTES
Vresion 71
Version 71 of VSHIELD adds a lock feature to prevent users
from continuing to use the system if a virus is found. When the
/LOCK option is used, VSHIELD will freeze the system after
displaying a message identifying the virus and the virus location.
Version 71 of VSHIELD adds sixteen new viruses, bringing the
total number of known computer viruses to 157, and total number of
virus variants to 260.