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1992-07-08
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SENTRY Version 3.0 Beta
Copyright (C) 1988-1992 by McAfee Associates.
All Rights Reserved
Documentation by Aryeh Goretsky
McAfee Associates (408) 988-3832 office
3350 Scott Blvd., Bldg. 14 (408) 970-9727 fax
Santa Clara, CA 95054-3107 (408) 988-4004 BBS (32 lines)
U.S.A. USR HST/v.32/v.42bis/MNP1-5
CompuServe GO VIRUSFORUM
InterNet mcafee@netcom.COM
TABLE OF CONTENTS
SYNOPSIS . . . . . . . . . . . . . . . . . . . . . . . 2
What is SENTRY
System Requirements
AUTHENTICITY . . . . . . . . . . . . . . . . . . . . . 3
Verifying SENTRY
INSTALLATION . . . . . . . . . . . . . . . . . . . . . 4
How to install SENTRY on your system
RE-CONFIGURATION . . . . . . . . . . . . . . . . . . . 5
How to update SENTRY's log file
OPERATION. . . . . . . . . . . . . . . . . . . . . . . 5
How SENTRY works
IF A VIRUS IS FOUND. . . . . . . . . . . . . . . . . . 6
What to do if a virus is found
How to remove partition table, boot, and file viruses
EXTRA PRECAUTIONS. . . . . . . . . . . . . . . . . . . 6
Making a backup copy of SENTRY
SENTRY Version 3.0 Beta Page 2
WARNING!
This product is in BETA test stage only! McAfee Associates is
not liable for any damages resulting from the use of this product.
The disclaimer of liability for this BETA stage product shall not
infer an acceptance of liability for damages for any product that may
descend from this BETA product. Sorry folks, but the lawyers need it!
SYNOPSIS
SENTRY is a computer virus detection and location program
for IBM PC and compatible systems. The SENTRY installation
program creates a log file of the system. This log file is a
snapshot of all system areas that are susceptible to virus
attacks. SENTRY compares the system against its log file using
a high speed search algorithm.
If a virus does enter your system, SENTRY will report the
specific system area or program files that have been infected.
The VIRUSCAN and CLEAN-UP programs can then be used to determine
if it is a known virus and remove it.
Since SENTRY detects viruses generically, i.e., looking for
the changes that a virus must make to infect a system, it works
as an 'early-warning' mechanism for corporate environments where
rapid distribution of virus-scanning software cannot be easily
accomplished or on networked PC's that do not have enough RAM
for memory resident programs.
SENTRY executes in two phases: An initial install phase and
subsequent check phase.
The initial install phase logs the system's hardware and
software parameters - including the initial interrupt vector
states, master boot record (partition table), boot sector, and
all .COM and .EXE program files on the hard disk. File header
information, initial program load instructions, branch
addresses, and other information are also logged for each
program on the disk.
The subsequent check phase executes when SENTRY is
run--each time the system is powered on or rebooted. SENTRY
then checks the system for signs of infection.
SENTRY is fully effective in detecting all viruses,
including partition table and boot sector viruses, file
infectors and stealth viruses. It provides a timely and nearly
foolproof indication of infection.
SENTRY works on any PC with 256Kb or more of memory running
DOS 2.11 or above.
SENTRY Version 3.0 Beta Page 3
AUTHENTICITY
SENTRY is packaged with the VALIDATE program to ensure the
integrity of the SENTRY.EXE and INSTALL.EXE file. The
VALIDATE.DOC file tells how to use VALIDATE. VALIDATE can be
used to check subsequent versions of SENTRY for tampering.
The validation results for SENTRY Version 3 should be:
FILE NAME: SENTRY.EXE INSTALL.EXE
SIZE: 30,414 17,962
DATE: 07-06-1992 07-06-1992
FILE AUTHENTICATION
Check Method 1: 3BFD 792C
Check Method 2: 036C 0622
If your copy of SENTRY differs, it may have been damaged.
Always obtain your copy of SENTRY from a known source. The
latest version of SENTRY and validation data can be obtained
from McAfee Associates' bulletin board system at
(408) 988-4004 or from the Computer Virus Help Forum on
CompuServe (GO VIRUSFORUM).
Beginning with Version 72, all of McAfee Associates'
VIRUSCAN series are archived with PKWare's PKZIP Authentic File
Verification. If you do not see an "-AV" after every file is
unzipped and receive the "Authentic Files Verified! # NWN405
Zip Source: McAFEE ASSOCIATES" message when you unzip the files
then do not use them. If your version of PKUNZIP does not have
verification ability, then this message may not be displayed.
Please contact us if you believe tampering has occured to the
.ZIP file.
SENTRY Version 3.0 Beta Page 4
INSTALLATION
NOTE: The SENTRY installation phase takes a longer amount of
time then the check phase. This is because SENTRY has
to compute a log entry for each system area.
SENTRY installs on the primary (bootable) partition of your
hard disk drive. If your system contains multiple hard drives,
then they may also be logged by SENTRY.
To install SENTRY on a system, type:
INSTALL logfile d1:..d26: [/Q] [/F]
[/S <pathspec_1>...<pathspec_n>] [/C]
[/NOI] [/NOB] [/NOP]
Options are:
'logfile' - Directory path and filename of the SENTRY log
file to create. If no name is given, then
C:\SENTRY3.LOG is used as the default log.
d1:...d26: - Drives to be logged. If no drive(s) is
specified, then C: is used as the default
drive.
/C - Perform full cryptographic checksumming of
files during the installation and check phases.
If /C is not specified, cryptographic
checksumming is only performed during
installation.
/F - Do not allow user to continue if change is
found. If /F is not specified, SENTRY will
allow the user to continue after changes have
been reported.
/NOB - Do not store boot sector check in log.
/NOI - Do not store interrupt vector check in log.
/NOP - Do not store partition table check in log.
/Q - Quiet mode, no messages displayed on the screen
unless a change is found. If /Q is not
specified, then SENTRY will tell which area of
the system is checking as it runs.
/S pathspecs - Filename(s) or subdirectory(ies) to skip when
installing SENTRY.
SENTRY Version 3.0 Beta Page 5
Once the INSTALL program has started, you will be prompted
to remove all floppy disks from the disk drives. Now you must
remove any diskettes from the A: drive and other disk drives.
Once the disks have been removed, press any key to continue the
installation. The PC will reboot and SENTRY will create its
log file and install SENTRY.EXE as the first program in your
AUTOEXEC.BAT file.
NOTE: SENTRY.EXE MUST REMAIN THE FIRST INSTRUCTION IN YOUR
AUTOEXEC.BAT FILE IN ORDER TO OPERATE CORRECTLY.
The SENTRY installation process may take 10 minutes or more
for systems with large numbers of files - the default check
function, however, will execute many times faster. After the
installation has completed, the system will reboot in order to
return the system to its state prior to installation.
The SENTRY log file will take approximately 175 bytes for
each executable program on the disk(s).
RE-CONFIGURATION
SENTRY checks the system for modifications each time the
system is powered on or re-booted. If any system area has
changed, SENTRY will flag the changed areas as possibly
infected. The following system modifications will cause SENTRY
to issue a warning:
- Installing a new version of DOS
- Removing or adding a device driver to CONFIG.SYS
- Deleting a program
- Replacing a program with a different version
If any of the above have occurred, SENTRY will prompt the
user for authorization to include the changes in the log file.
The log file will be updated to include the system
modifications. This will prevent SENTRY from false alarming
during subsequent executions. To prevent changes from being
made to the log file, install SENTRY with the /F switch.
OPERATION
The SENTRY check function compares the current state of
your system to the original "snapshot" state, checking
executable programs on your system for modifications caused by
viral infection. The algorithm is able to do this in a
reasonable amount of time due to a selective logging function.
This logging function logs only those segments of program code
that would be affected by virus attack. SENTRY also checks the
partition table, boot sector, and all system interrupt vectors
for modifications.
SENTRY Version 3.0 Beta Page 6
The SENTRY check function executes each time the system is
powered on or re-booted. If a discrepancy in any area of the
system is noted, the check function will pause and display a
message identifying the system area and the discrepancy. If no
discrepancies are found, the check function will terminate with
an OK message. The check function will require about 10
seconds for each 100 executable programs stored on your hard
disk.
IF A VIRUS IS FOUND
NOTE: When SENTRY reports a virus, note the name(s) of the
infected programs or system areas. Immediately power
down the system, reboot the system from the original DOS
distribution diskette (or a write-protected copy), and
then run the VIRUSCAN program to identify the virus.
Before removing a virus, back up any critical files such
as data or source code.
Partition table infectors modify or replace the hard disk's
partition table. To remove a partition table infector, run the
CLEAN-UP virus disinfection program, or use the FDISK command
with the undocumented /MBR switch to rewrite the partition table
(MS-DOS 5.00 only).
Boot sector infectors replace or modify a disk's boot
sector. To remove a boot sector infector, run the CLEAN-UP
virus disinfection program, or use the SYS command to replace
the DOS boot sector. See your DOS manual for instructions on
using the SYS command.
File infectors modify the beginning instructions of a
program. To remove a file infector, run the CLEAN-UP virus
disinfection program, or delete the file and replace it with a
clean copy.
If SENTRY detects an infection, and you have any questions
about the program, please contact McAfee Associates or any of
our Authorized Agents listed in the AGENTS.TXT file.
EXTRA PRECAUTIONS
To prevent any possibility of viral tampering with the
SENTRY program and log file, you should copy the SENTRY.EXE
and log files from your hard disk to a backup floppy after
installation. Write protect the floppy to prevent it from
becoming infected.
NOTE:
This software uses the RSA Data Security, Inc. MD4 Message-Digest
Algorithm. The MD4 algorithm is Copyright (C) 1991-2, RSA Data
Security, Inc. Created 1991. All rights reserved.