McAfee AVDCDE-AA-AA - Active Virus Defense Suite User manual

McAfee VirusScan
Anti-Virus Software
User’s Guide
Version 4.5

COPYRIGHT
Copyright © 1995-2000 Networks Associates Technology, Inc. All Rights Reserved. No part of
this publication may be reproduced, transmitted, transcribed, stored in a retrieval system, or
translated into any language in any form or by any means without the written permission of
Networks Associates Technology, Inc., or its suppliers or affiliate companies.
TRADEMARK ATTRIBUTIONS
* ActiveHelp, Bomb Shelter, Building a World of Trust, CipherLink, Clean-Up, Cloaking, CNX,
Compass 7, CyberCop, CyberMedia, Data Security Letter, Discover, Distributed Sniffer System, Dr
Solomon’s, Enterprise Secure Cast, First Aid, ForceField, Gauntlet, GMT, GroupShield, HelpDesk,
Hunter, ISDN Tel/Scope, LM 1, LANGuru, Leading Help Desk Technology, Magic Solutions,
MagicSpy, MagicTree, Magic University, MagicWin, MagicWord, McAfee, McAfee Associates,
MoneyMagic, More Power To You, Multimedia Cloaking, NetCrypto, NetOctopus, NetRoom,
NetScan, Net Shield, NetShield, NetStalker, Net Tools, Network Associates, Network General, Network
Uptime!, NetXRay, Nuts & Bolts, PC Medic, PCNotary, PGP, PGP (Pretty Good Privacy),
PocketScope, Pop-Up, PowerTelnet, Pretty Good Privacy, PrimeSupport, RecoverKey,
RecoverKey-International, ReportMagic, RingFence, Router PM, Safe & Sound, SalesMagic,
SecureCast, Service Level Manager, ServiceMagic, Site Meter, Sniffer, SniffMaster, SniffNet, Stalker,
Statistical Information Retrieval (SIR), SupportMagic, Switch PM, TeleSniffer, TIS, TMach, TMeg,
Total Network Security, Total Network Visibility, Total Service Desk, Total Virus Defense, T-POD,
Trusted Mach, Trusted Mail, Uninstaller, Virex, Virex-PC, Virus Forum, ViruScan, VirusScan,
VShield, WebScan, WebShield, WebSniffer, WebStalker WebWall, and ZAC 2000 are registered
trademarks of Network Associates and/or its affiliates in the US and/or other countries. All
other registered and unregistered trademarks in this document are the sole property of their
respective owners.
LICENSE AGREEMENT
NOTICE TO ALL USERS: FOR THE SPECIFIC TERMS OF YOUR LICENSE TO USE THE
SOFTWARE THAT THIS DOCUMENTATION DESCRIBES, CONSULT THE README.1ST,
LICENSE.TXT, OR OTHER LICENSE DOCUMENT THAT ACCOMPANIES YOUR
SOFTWARE, EITHER AS A TEXT FILE OR AS PART OF THE SOFTWARE PACKAGING. IF
YOU DO NOT AGREE TO ALL OF THE TERMS SET FORTH THEREIN, DO NOT INSTALL
THE SOFTWARE. IF APPLICABLE, YOU MAY RETURN THE PRODUCT TO THE PLACE OF
PURCHASE FOR A FULL REFUND.
Issued March 2000/VirusScan v4.5.0

User’s Guide iii
Table of Contents
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
What happened? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
Why worry? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
Where do viruses come from? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .x
Virus prehistory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .x
Viruses and the PC revolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi
On the frontier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiv
Where next? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvi
How to protect yourself . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xvii
How to contact McAfee and Network Associates . . . . . . . . . . . . . . . . . . . . xviii
Customer service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xviii
Technical support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xix
Download support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xx
Network Associates training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xx
Comments and feedback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xx
Reporting new items for anti-virus data file updates . . . . . . . . . . . . . . xxi
International contact information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xxii
Chapter 1. About VirusScan Software . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Introducing VirusScan anti-virus software . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
How does VirusScan software work? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
What comes with VirusScan software? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
What’s new in this release? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
Chapter 2. Installing VirusScan Software . . . . . . . . . . . . . . . . . . . . . . . . 37
Before you begin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37
System requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37
Other recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37
Preparing to install VirusScan software . . . . . . . . . . . . . . . . . . . . . . . . .38
Installation options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38
Installation steps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39
Using the Emergency Disk Creation utility . . . . . . . . . . . . . . . . . . . . . . .51
Determining when you must restart your computer . . . . . . . . . . . . . . . .56

Table of Contents
iv McAfee VirusScan Anti-Virus Software
Testing your installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57
Modifying or removing your VirusScan installation . . . . . . . . . . . . . . . .58
Chapter 3. Removing Infections From Your System . . . . . . . . . . . . . . . 61
If you suspect you have a virus... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61
Deciding when to scan for viruses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64
Recognizing when you don’t have a virus . . . . . . . . . . . . . . . . . . . . . . . . . . . .65
Understanding false detections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66
Responding to viruses or malicious software . . . . . . . . . . . . . . . . . . . . . . . . .67
Submitting a virus sample . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .78
Using the SendVirus utility to submit a file sample . . . . . . . . . . . . . . . .78
Capturing boot sector, file-infecting, and macro viruses . . . . . . . . . . . .81
Chapter 4. Using the VShield Scanner . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
What does the VShield scanner do? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .87
Why use the VShield scanner? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .88
Browser and e-mail client support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .89
Enabling or starting the VShield scanner . . . . . . . . . . . . . . . . . . . . . . . . . . . . .90
Using the VShield configuration wizard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .95
Setting VShield scanner properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99
Using the VShield shortcut menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .155
Disabling or stopping the VShield scanner . . . . . . . . . . . . . . . . . . . . . . . . . .155
Tracking VShield software status information . . . . . . . . . . . . . . . . . . . . . . . .161
Chapter 5. Using the VirusScan application . . . . . . . . . . . . . . . . . . . . . 163
What is the VirusScan application? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .163
Why use the VirusScan application? . . . . . . . . . . . . . . . . . . . . . . . . . . .164
Starting the VirusScan application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .165
Configuring the VirusScan Classic interface . . . . . . . . . . . . . . . . . . . . . . . . .171
Configuring the VirusScan Advanced interface . . . . . . . . . . . . . . . . . . . . . .176
Chapter 6. Creating and Configuring Scheduled Tasks . . . . . . . . . . . . 193
What does VirusScan Console do? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .193
Why schedule scan operations? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .193
Starting the VirusScan Console . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .194

User’s Guide v
Table of Contents
Using the Console window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .196
Working with default tasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .198
Working with the VShield task . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .200
Working with the AutoUpgrade and AutoUpdate tasks . . . . . . . . . . . .201
Creating new tasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .202
Enabling tasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .206
Checking task status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .208
Configuring VirusScan application options . . . . . . . . . . . . . . . . . . . . . . . . . .210
Chapter 7. Updating and Upgrading VirusScan Software . . . . . . . . . . 229
Developing an updating strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .229
Update and upgrade methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .230
Understanding the AutoUpdate utility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .232
Configuring the AutoUpdate Utility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .233
Understanding the AutoUpgrade utility . . . . . . . . . . . . . . . . . . . . . . . . . . . . .242
Configuring the AutoUpgrade utility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .243
Using the AutoUpgrade and SuperDAT utilities together . . . . . . . . . .252
Chapter 8. Using Specialized Scanning Tools . . . . . . . . . . . . . . . . . . . 255
Scanning Microsoft Exchange and Outlook mail . . . . . . . . . . . . . . . . . . . . .255
When and why you should use the E-Mail Scan extension . . . . . . . . .255
Using the E-Mail Scan extension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .256
Configuring the E-Mail Scan extension . . . . . . . . . . . . . . . . . . . . . . . . .257
Scanning cc:Mail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .271
Using the ScreenScan utility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .271
Chapter 9. Using VirusScan Utilities . . . . . . . . . . . . . . . . . . . . . . . . . . . 279
Understanding the VirusScan control panel . . . . . . . . . . . . . . . . . . . . . . . . .279
Opening the VirusScan control panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .279
Choosing VirusScan control panel options . . . . . . . . . . . . . . . . . . . . . . . . . .280
Using the Alert Manager Client Configuration utility . . . . . . . . . . . . . . . . . .283
VirusScan software as an Alert Manager client . . . . . . . . . . . . . . . . . . . . . . .284
Configuring the Alert Manager client utility . . . . . . . . . . . . . . . . . . . . . . . . . .284

Table of Contents
vi McAfee VirusScan Anti-Virus Software
Appendix A. Default Vulnerable and Compressed File Extensions . . 289
Adding file name extensions for scanning . . . . . . . . . . . . . . . . . . . . . . . . . . .289
Current list of vulnerable file name extensions . . . . . . . . . . . . . . . . . . . . . . .290
Current list of compressed files scanned . . . . . . . . . . . . . . . . . . . . . . . . . . .294
Appendix B. Network Associates Support Services . . . . . . . . . . . . . . 297
Adding value to your McAfee product . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .297
PrimeSupport options for corporate customers . . . . . . . . . . . . . . . . . .297
Ordering a corporate PrimeSupport plan . . . . . . . . . . . . . . . . . . . . . . .300
PrimeSupport options for home users . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .302
How to reach international home user support . . . . . . . . . . . . . . . . . . .304
Ordering a PrimeSupport plan for home users . . . . . . . . . . . . . . . . . . .304
Network Associates consulting and training . . . . . . . . . . . . . . . . . . . . . . . . .305
Professional Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .305
Total Education Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .306
Appendix C. Using the SecureCast Service to Get New Data Files . . 307
Introducing the SecureCast service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .307
Why should I update my data files? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .308
Which data files does the SecureCast service deliver? . . . . . . . . . . . .308
Installing the BackWeb client and SecureCast service . . . . . . . . . . . . . . . . .309
System requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .309
Troubleshooting the Enterprise SecureCast service . . . . . . . . . . . . . .319
Unsubscribing from the SecureCast service . . . . . . . . . . . . . . . . . . . . .319
Support resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .319
SecureCast service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .319
BackWeb client . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .320
Appendix D. Understanding iDAT Technology . . . . . . . . . . . . . . . . . . . 321
Understanding incremental .DAT files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .321
How does iDAT updating work? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .322
What does McAfee post each week? . . . . . . . . . . . . . . . . . . . . . . . . . . .323
Best practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .324
Frequently asked questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .325
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327

User’s Guide vii
Preface
What happened?
If you’ve ever lost important files stored on your hard disk, watched in dismay
as your computer ground to a halt only to display a prankster’s juvenile
greeting on your monitor, or found yourself having to apologize for abusive
e-mail messages you never sent, you know first-hand how computer viruses
and other harmful programs can disrupt your productivity. If you haven’t yet
suffered from a virus “infection,” count yourself lucky. But with more than
50,000 known viruses in circulation capable of attacking Windows- and
DOS-based computer systems, it really is only a matter of time before you do.
The good news is that of those thousands of circulating viruses, only a small
proportion have the means to do real damage to your data. In fact, the term
“computer virus” identifies a broad array of programs that have only one
feature in common: they “reproduce” themselves automatically by attaching
themselves to host software or disk sectors on your computer, usually without
your knowledge. Most viruses cause relatively trivial problems, ranging from
the merely annoying to the downright insignificant. Often, the primary
consequence of a virus infection is the cost you incur in time and effort to track
down the source of the infection and eradicate all of its traces.
Why worry?
So why worry about virus infections, if most attacks do little harm? The
problem is twofold. First, although relatively few viruses have destructive
effects, that fact says nothing about how widespread the malicious viruses are.
In many cases, viruses with the most debilitating effects are the hardest to
detect—the virus writer bent on causing harm will take extra steps to avoid
discovery. Second, even “benign” viruses can interfere with the normal
operation of your computer and can cause unpredictable behavior in other
software. Some viruses contain bugs, poorly written code, or other problems
severe enough to cause crashes when they run. Other times, legitimate
software has problems running when a virus has, intentionally or otherwise,
altered system parameters or other aspects of the computing environment.
Tracking down the source of resulting system freezes or crashes can drain time
and money from more productive activities.
Beyond these problems lies a problem of perception: once infected, your
computer can serve as a source of infection for other computers. If you
regularly exchange data with colleagues or customers, you could unwittingly
pass on a virus that could do more damage to your reputation or your dealings
with others than it does to your computer.

Preface
viii McAfee VirusScan Anti-Virus Software
The threat from viruses and other malicious software is real, and it is growing
worse. Some estimates have placed the total worldwide cost in time and lost
productivity for merely detecting and cleaning virus infections at more than
$10 billion per year, a figure that doesn’t include the costs of data loss and
recovery in the wake of attacks that destroyed data.
Where do viruses come from?
As you or one of your colleagues recovers from a virus attack or hears about
new forms of malicious software appearing in commonly used programs,
you’ve probably asked yourself a number of questions about how we as
computer users got to this point. Where do viruses and other malicious
programs come from? Who writes them? Why do those who write them seek
to interrupt workflows, destroy data, or cost people the time and money
necessary to eradicate them? What can stop them?
Why did this happen to me?
It probably doesn’t console you much to hear that the programmer who wrote
the virus that erased your hard disk’s file allocation table didn’t target you or
your computer specifically. Nor will it cheer you up to learn that the virus
problem will probably always be with us. But knowing a bit about the history
of computer viruses and how they work can help you better protect yourself
against them.
Virus prehistory
Historians have identified a number of programs that incorporated features
now associated with virus software. Canadian researcher and educator Robert
M. Slade traces virus lineage back to special-purpose utilities used to reclaim
unused file space and perform other useful tasks in the earliest networked
computers. Slade reports that computer scientists at a Xerox Corporation
research facility called programs like these “worms,”a term coined after the
scientists noticed “holes”in printouts from computer memory maps that
looked as though worms had eaten them. The term survives to this day to
describe programs that make copies of themselves, but without necessarily
using host software in the process.
A strong academic tradition of computer prank playing most likely
contributed to the shift away from utility programs and toward more
malicious uses of the programming techniques found in worm software.
Computer science students, often to test their programming abilities, would
construct rogue worm programs and unleash them to “fight”against each
other, competing to see whose program could “survive”while shutting down
rivals. Those same students also found uses for worm programs in practical
jokes they played on unsuspecting colleagues.

User’s Guide ix
Preface
Some of these students soon discovered that they could use certain features of
the host computer’s operating system to give them unauthorized access to
computer resources. Others took advantage of users who had relatively little
computer knowledge to substitute their own programs—written for their own
purposes—in place of common or innocuous utilities. These unsophisticated
users would run what they thought was their usual software only to find their
files erased, to have their account passwords stolen, or to suffer other
unpleasant consequences. Such “Trojan horse”programs or “Trojans,”so
dubbed for their metaphorical resemblance to the ancient Greek gift to the city
of Troy, remain a significant, and growing, threat to computer users today.
Viruses and the PC revolution
What we now think of as true computer viruses first appeared, according to
Robert Slade, soon after the first personal computers reached the mass market
in the early 1980s. Other researchers date the advent of virus programs to 1986,
with the appearance of the “Brain”virus. Whichever date has the better claim,
the link between the virus threat and the personal computer is not
coincidental.
The new mass distribution of computers meant that viruses could spread to
many more hosts than before, when a comparatively few, closely guarded
mainframe systems dominated the computing world from their bastions in
large corporations and universities. Nor did the individual users who bought
PCs have much use for the sophisticated security measures needed to protect
sensitive data in those environments. As further catalyst, virus writers found
it relatively easy to exploit some PC technologies to serve their own ends.
Boot-sector viruses
Early PCs, for example, “booted”or loaded their operating systems from
floppy disks. The authors of the Brain virus discovered that they could
substitute their own program for the executable code present on the boot
sector of every floppy disk formatted with Microsoft’s MS-DOS, whether or
not it included system files. Users thereby loaded the virus into memory every
time they started their computers with any formatted disk in their floppy
drives. Once in memory, a virus can copy itself to boot sectors on other floppy
or hard disks. Those who unintentionally loaded Brain from an infected
floppy found themselves reading an ersatz “advertisement”for a computer
consulting company in Pakistan.
With that advertisement, Brain pioneered another characteristic feature of
modern viruses: the payload. The payload is the prank or malicious behavior
that, if triggered, causes effects that range from annoying messages to data
destruction. It’s the virus characteristic that draws the most attention—many
virus authors now write their viruses specifically to deliver their payloads to
as many computers as possible.

Preface
x McAfee VirusScan Anti-Virus Software
For a time, sophisticated descendants of this first boot-sector virus represented
the most serious virus threat to computer users. Variants of boot sector viruses
also infect the Master Boot Record (MBR), which stores the partition
information your computer needs to figure out where to find each of your
hard disk partitions and the boot sector itself.
Realistically, nearly every step in the boot process, from reading the MBR to
loading the operating system, is vulnerable to virus sabotage. Some of the
most tenacious and destructive viruses still include the ability to infect your
computer’s boot sector or MBR among their repertoire of tricks. Among other
advantages, loading at boot time can give a virus a chance to do its work before
your anti-virus software has a chance to run. Many McAfee anti-virus
products anticipate this possibility by allowing you to create an emergency
disk you can use to boot your computer and remove infections.
But most boot sector and MBR viruses had a particular weakness: they spread
by means of floppy disks or other removable media, riding concealed in that
first track of disk space. As fewer users exchanged floppy disks and as
software distribution came to rely on other media, such as CD-ROMs and
direct downloading from the Internet, other virus types eclipsed the boot
sector threat. But it’s far from gone—many later-generation viruses routinely
incorporate functions that infect your hard disk boot sector or MBR, even if
they use other methods as their primary means of transmission.
Those same viruses have also benefitted from several generations of evolution,
and therefore incorporate much more sophisticated infection and concealment
techniques that make it far from simple to detect them, even when they hide
in relatively predictable places.
File infector viruses
At about the same time as the authors of the Brain virus found vulnerabilities
in the DOS boot sector, other virus writers found out how to use other
software to help replicate their creations. An early example of this type of virus
showed up in computers at Lehigh University in Pennsylvania. The virus
infected part of the DOS command interpreter COMMAND.COM, which it
used to load itself into memory. Once there, it spread to other uninfected
COMMAND.COM files each time a user entered any standard DOS command
that involved disk access. This limited its spread to floppy disks that
contained, usually, a full operating system.
Later viruses quickly overcame this limitation, sometimes with fairly clever
programming. Virus writers might, for instance, have their virus add its code
to the beginning of an executable file, so that when users start a program, the
virus code executes immediately, then transfers control back to the legitimate
software, which runs as though nothing unusual has happened. Once it
activates, the virus “hooks”or “traps”requests that legitimate software makes
to the operating system and substitutes its own responses.

User’s Guide xi
Preface
Particularly clever viruses can even subvert attempts to clear them from
memory by trapping the CTRL+ALT+DEL keyboard sequence for a warm
reboot, then faking a restart. Sometimes the only outward indication that
anything on your system is amiss—before any payload detonates, that
is—might be a small change in the file size of infected legitimate software.
Stealth, mutation, encryption, and polymorphic techniques
Unobtrusive as they might be, changes in file size and other scant evidence of
a virus infection usually gives most anti-virus software enough of a scent to
locate and remove the offending code. One of the virus writer’s principal
challenges, therefore, is to find ways to hide his or her handiwork. The earliest
disguises were a mixture of innovative programming and obvious giveaways.
The Brain virus, for instance, redirected requests to see a disk’s boot sector
away from the actual location of the infected sector to the new location of the
boot files, which the virus had moved. This “stealth”capability enabled this
and other viruses to hide from conventional search techniques.
Because viruses needed to avoid continuously reinfecting host systems—
doing so would quickly balloon an infected file’s size to easily detectable
proportions or would consume enough system resources to point to an
obvious culprit—their authors also needed to tell them to leave certain files
alone. They addressed this problem by having the virus write a characteristic
byte sequence or, in 32-bit Windows operating systems, create a particular
registry key that would flag infected files with the software equivalent of a “do
not disturb”sign. Although that kept the virus from giving itself away
immediately, it opened the way for anti-virus software to use the “do not
disturb”sequence itself, along with other characteristic patterns that the virus
wrote into files it infected, to spot its “code signature.”Most anti-virus
vendors now compile and regularly update a database of virus “definitions”
that their products use to recognize those code signatures in the files they scan.
In response, virus writers found ways to conceal the code signatures. Some
viruses would “mutate”or transform their code signatures with each new
infection. Others encrypted themselves and, as a result, their code signatures,
leaving only a couple of bytes to use as a key for decryption. The most
sophisticated new viruses employed stealth, mutation and encryption to
appear in an almost undetectable variety of new forms. Finding these
“polymorphic”viruses required software engineers to develop very elaborate
programming techniques for anti-virus software.

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xii McAfee VirusScan Anti-Virus Software
Macro viruses
By 1995 or so, the virus war had come to something of a standstill. New viruses
appeared continuously, prompted in part by the availability of ready-made
virus “kits”that enabled even some non-programmers to whip up a new virus
in no time. But most existing anti-virus software easily kept pace with updates
that detected and disposed of the new virus variants, which consisted
primarily of minor tweaks to well-known templates.
But 1995 marked the emergence of the Concept virus, which added a new and
surprising twist to virus history. Before Concept, most virus researchers
thought of data files—the text, spreadsheet, or drawing documents created by
the software you use—as immune to infection. Viruses, after all, are programs
and, as such, needed to run in the same way executable software did in order
to do their damage. Data files, on the other hand, simply stored information
that you entered when you worked with your software.
That distinction melted away when Microsoft began adding macro
capabilities to Word and Excel, the flagship applications in its Office suite.
Using the stripped-down version of its Visual Basic language included with
the suite, users could create document templates that would automatically
format and add other features to documents created with Word and Excel.
Other vendors quickly followed suit with their products, either using a
variation of the same Microsoft macro language or incorporating one of their
own. Virus writers, in turn, seized the opportunity that this presented to
conceal and spread viruses in documents that you, the user, created yourself.
The exploding popularity of the Internet and of e-mail software that allowed
users to attach files to messages ensured that macro viruses would spread very
quickly and very widely. Within a year, macro viruses became the most potent
virus threat ever.
On the frontier
Even as viruses grew more sophisticated and continued to threaten the
integrity of computer systems we all had come to depend upon, still other
dangers began to emerge from an unexpected source: the World Wide Web.
Once a repository of research papers and academic treatises, the web has
transformed itself into perhaps the most versatile and adaptable medium ever
invented for communication and commerce.
Because its potential seems so vast, the web has attracted the attention and the
developmental energies of nearly every computer-related company in the
industry.

User’s Guide xiii
Preface
Convergences in the technologies that have resulted from this feverish pace of
invention have given website designers tools they can use to collect and
display information in ways never previously available. Websites soon sprang
up that could send and receive e-mail, formulate and execute queries to
databases using advanced search engines, send and receive live audio and
video, and distribute data and multimedia resources to a worldwide audience.
Much of the technology that made these features possible consisted of small,
easily downloaded programs that interact with your browser software and,
sometimes, with other software on your hard disk. This same avenue served
as an entry point into your computer system for other—less benign—
programs to use for their own purposes.
Java, ActiveX, and scripted objects
These programs, whether beneficial or harmful, come in a variety of forms.
Some are special-purpose miniature applications, or “applets,”written in Java,
a programming language first developed by Sun Microsystems. Others are
developed using ActiveX, a Microsoft technology that programmers can use
for similar purposes.
Both Java and ActiveX make extensive use of prewritten software modules, or
“objects,”that programmers can write themselves or take from existing
sources and fashion into the plug-ins, applets, device drivers and other
software needed to power the web. Java objects are called “classes,”while
ActiveX objects are called “controls.”The principle difference between them
lies in how they run on the host system. Java applets run in a Java “virtual
machine”designed to interpret Java programming and translate it into action
on the host machine, while ActiveX controls run as native Windows software
that links and passes data among other Windows programs.
The overwhelming majority of these objects are useful, even necessary, parts
of any interactive website. But despite the best efforts of Sun and Microsoft
engineers to design security measures into them, determined programmers
can use Java and ActiveX tools to plant harmful objects on websites, where
they can lurk until visitors unwittingly allow them access to vulnerable
computer systems.
Unlike viruses, harmful Java and ActiveX objects usually don’t seek to
replicate themselves. The web provides them with plenty of opportunities to
spread to target computer systems, while their small size and innocuous
nature makes it easy for them to evade detection. In fact, unless you tell your
web browser specifically to block them, Java and ActiveX objects download to
your system automatically whenever you visit a website that hosts them.

Preface
xiv McAfee VirusScan Anti-Virus Software
Instead, harmful objects exist to deliver their equivalent of a virus payload.
Programmers have written objects, for example, that can read data from your
hard disk and send it back to the website you visited, that can “hijack”your
e-mail account and send out offensive messages in your name, or that can
watch data that passes between your computer and other computers.
Even more powerful agents have begun to appear in applications that run
directly from websites you visit. JavaScript, a scripting language with a name
similar to the unrelated Java language, first appeared in Netscape Navigator,
with its implementation of version 3.2 of the Hyper Text Markup Language
(HTML) standard. Since its introduction, JavaScript has grown tremendously
in capability and power, as have the host of other scripting technologies that
have followed it—including Microsoft VBScript and Active Server Pages,
Allaire Cold Fusion, and others. These technologies now allow software
designers to create fully realized applications that run on web servers, interact
with databases and other data sources, and directly manipulate features in the
web browser and e-mail client software running on your computer.
As with Java and ActiveX objects, significant security measures exist to
prevent malicious actions, but virus writers and security hackers have found
ways around these. Because the benefits these innovations bring to the web
generally outweigh the risks, however, most users find themselves calculating
the tradeoffs rather than shunning the technologies.
Where next?
Malicious software has even intruded into areas once thought completely out
of bounds. Users of the mIRC Internet Relay Chat client, for example, have
reported encountering viruses constructed from the mIRC scripting language.
The chat client sends script viruses as plain text, which would ordinarily
preclude them from infecting systems, but older versions of the mIRC client
software would interpret the instructions coded into the script and perform
unwanted actions on the recipient’s computer.
The vendors moved quickly to disable this capability in updated versions of
the software, but the mIRC incident illustrates the general rule that where a
way exists to exploit a software security hole, someone will find it and use it.
Late in 1999, another virus writer demonstrated this rule yet again with a
proof-of-concept virus called VBS/Bubbleboy that ran directly within the
Microsoft Outlook e-mail client by hijacking its built-in VBScript support. This
virus crossed the once-sharp line that divided plain-text e-mail messages from
the infectable attachments they carried. VBS/Bubbleboy didn’t even require
you to open the e-mail message—simply viewing it from the Outlook preview
window could infect your system.

User’s Guide xv
Preface
How to protect yourself
McAfee anti-virus software already gives you an important bulwark against
infection and damage to your data, but anti-virus software is only one part of
the security measures you should take to protect yourself. Anti-virus software,
moreover, is only as good as its latest update. Because as many as 200 to 300
viruses and variants appear each month, the virus definition (.DAT) files that
enable McAfee software to detect and remove viruses can get quickly
outdated. If you have not updated the files that originally came with your
software, you could risk infection from newly emerging viruses. McAfee has,
however, assembled the world’s largest and most experienced anti-virus
research staff in its Anti-Virus Emergency Response Team (AVERT)*. This
means that the files you need to combat new viruses appear as soon as—and
often before—you need them.
Most other security measures are common sense—checking disks you receive
from unknown or questionable sources, either with anti-virus software or
some kind of verification utility, is always a good idea. Malicious
programmers have gone so far as to mimic the programs you trust to guard
your computer, pasting a familiar face on software with a less-than-friendly
purpose. Neither McAfee nor any other anti-virus software, however, can
detect when someone substitutes an as-yet unidentified Trojan horse or other
malicious program for one of your favorite shareware or commercial
utilities—that is, until after the fact.
Web and Internet access poses its own risks. VirusScan* anti-virus software
gives you the ability to block dangerous web sites so that users can’t
inadvertently download malicious software from known hazards; it also
catches hostile objects that get downloaded anyway. But having a top-notch
firewall in place to protect your network and implementing other network
security measures is a necessity when unscrupulous attackers can penetrate
your network from nearly any point on the globe, whether to steal sensitive
data or implant malicious code. You should also make sure that your network
is not accessible to unauthorized users, and that you have an adequate training
program in place to teach and enforce security standards. To learn about the
origin, behavior and other characteristics of particular viruses, consult the
Virus Information Library maintained on the AVERT website.
McAfee can provide you with other powerful software in the Active Virus
Defense* (AVD) and Total Virus Defense (TVD) suites, the most
comprehensive anti-virus solutions available. Related companies within the
Network Associates family provide other technologies that also help to protect
your network, including the PGP Security CyberCop product line, and the
Sniffer Technologies network monitoring product suite. Contact your
Network Associates representative, or visit the Network Associates website,
to find out how to enlist the power of these security solutions on your side.

Preface
xvi McAfee VirusScan Anti-Virus Software
How to contact McAfee and Network Associates
Customer service
On December 1, 1997, McAfee Associates merged with Network General
Corporation, Pretty Good Privacy, Inc., and Helix Software, Inc. to form
Network Associates, Inc. The combined Company subsequently acquired Dr
Solomon’s Software, Trusted Information Systems, Magic Solutions, and
CyberMedia, Inc.
A January 2000 company reorganization formed four independent business
units, each concerned with a particular product line. These are:
•Magic Solutions. This division supplies the Total Service desk product line
and related products
•McAfee. This division provides the Active Virus Defense product suite
and related anti-virus software solutions to corporate and retail customers.
•PGP Security. This division provides award-winning encryption and
security solutions, including the PGP data security and encryption product
line, the Gauntlet firewall product line, the WebShield E-ppliance
hardware line, and the CyberCop Scanner and Monitor product series.
•Sniffer Technologies. This division supplies the industry-leading Sniffer
network monitoring, reporting, and analysis utility and related software.
Network Associates continues to market and support the product lines from
each of the new independent business units. You may direct all questions,
comments, or requests concerning the software you purchased, your
registration status, or similar issues to the Network Associates Customer
Service department at the following address:
Network Associates Customer Service
4099 McEwan, Suite 500
Dallas, Texas 75244
U.S.A.
The department's hours of operation are 8:00 a.m. and 8:00 p.m. Central time,
Monday through Friday
Other contact information for corporate-licensed customers:
Phone: [phone]
Fax: [phone] (24-hour, Group III fax)
E-Mail: [e-mail]
Web: http://www.nai.com

User’s Guide xvii
Preface
Other contact information for retail-licensed customers:
Phone: [phone]
Fax: [phone] (24-hour, Group III fax)
E-Mail: [e-mail]
Web: http://www.mcafee.com/
Technical support
McAfee and Network Associates are famous for their dedication to customer
satisfaction. The companies have continued this tradition by making their sites
on the World Wide Web valuable resources for answers to technical support
issues. McAfee encourages you to make this your first stop for answers to
frequently asked questions, for updates to McAfee and Network Associates
software, and for access to news and virus information.
If you do not find what you need or do not have web access, try one of our
automated services.
If the automated services do not have the answers you need, contact Network
Associates at one of the following numbers Monday through Friday between
8:00 A.M. and 8:00 P.M. Central time to find out about Network Associates
technical support plans.
For corporate-licensed customers:
For retail-licensed customers:
This guide includes a summary of the PrimeSupport plans available to
McAfee customers. To learn more about plan features and other details, see
Appendix B, “Network Associates Support Services.”
World Wide Web http://www.nai.com/asp_set/services/technical_support
/tech_intro.asp
Internet [e-mail]
CompuServe GO NAI
America Online keyword MCAFEE
Phone [phone]
Fax [phone]
Phone [phone]
Fax [phone]

Preface
xviii McAfee VirusScan Anti-Virus Software
To provide the answers you need quickly and efficiently, the Network
Associates technical support staff needs some information about your
computer and your software. Please include this information in your
correspondence:
•Product name and version number
•Computer brand and model
•Any additional hardware or peripherals connected to your computer
•Operating system type and version numbers
•Network type and version, if applicable
•Contents of your AUTOEXEC.BAT, CONFIG.SYS, and system LOGIN
script
•Specific steps to reproduce the problem
Download support
To get help with navigating or downloading files from the Network Associates
or McAfee websites or FTP sites, call:
Network Associates training
For information about scheduling on-site training for any McAfee or Network
Associates product, call Network Associates Customer Service at:
[phone].
Comments and feedback
McAfee appreciates your comments and reserves the right to use any
information you supply in any way it believes appropriate without incurring
any obligation whatsoever. Please address your comments about McAfee
anti-virus product documentation to: McAfee, 20460 NW Von Neumann,
Beaverton, OR 97006-6942, U.S.A. You can also send faxed comments to
[phone] or e-mail to [e-mail].
Corporate customers [phone]
Retail customers [phone]

User’s Guide xix
Preface
Reporting new items for anti-virus data file updates
McAfee anti-virus software offers you the best available detection and
removal capabilities, including advanced heuristic scanning that can detect
new and unnamed viruses as they emerge. Occasionally, however, an entirely
new type of virus that is not a variation on an older type can appear on your
system and escape detection.
Because McAfee researchers are committed to providing you with effective
and up-to-date tools you can use to protect your system, please tell them about
any new Java classes, ActiveX controls, dangerous websites, or viruses that
your software does not now detect. Note that McAfee reserves the right to use
any information you supply as it deems appropriate, without incurring any
obligations whatsoever. Send your questions or virus samples to:
To report items to the McAfee European research office, use these e-mail
addresses:
To report items to the McAfee Asia-Pacific research office, or the office in
Japan, use one of these e-mail addresses:
[e-mail] Use this address to send questions or
virus samples to our North America
and South America offices
[e-mail] Use this address to send questions or
virus samples gathered with Dr
Solomon’s Anti-Virus Toolkit* software
to our offices in the United Kingdom
[e-mail] Use this address to send questions or
virus samples to our offices in Western
Europe
[e-mail] Use this address to send questions or
virus samples gathered with Dr
Solomon’s Anti-Virus Toolkit software
to our offices in Germany
[e-mail] Use this address to send questions or
virus samples to our offices in Japan
and East Asia
[e-mail] Use this address to send questions or
virus samples to our offices in Australia
and Southeast Asia

Preface
xx McAfee VirusScan Anti-Virus Software
International contact information
To contact Network Associates outside the United States, use the addresses,
phone numbers and fax numbers below.
Network Associates
Australia
Level 1, 500 Pacific Highway
St. Leonards, NSW
Sydney, Australia 2065
Phone: [phone]
Fax: [phone]
Network Associates
Austria
Pulvermuehlstrasse 17
Linz, Austria
Postal Code A-4040
Phone: [phone]
Fax: [phone]
Network Associates
Belgique
BDC Heyzel Esplanade, boîte 43
1020 Bruxelles
Belgique
Phone: [phone]
Fax: [phone]
Network Associates
do Brasil
Rua Geraldo Flausino Gomez 78
Cj. - 51 Brooklin Novo - São Paulo
SP - 04575-060 - Brasil
Phone: [phone]
Fax: [phone]
Network Associates
Canada
139 Main Street, Suite 201
Unionville, Ontario
Canada L3R 2G6
Phone: [phone]
Fax: [phone]
Network Associates
People’s Republic of China
New Century Office Tower, Room 1557
No. 6 Southern Road Capitol Gym
Beijing
People’s Republic of China 100044
Phone: [phone]
Fax: [phone]
Network Associates Denmark
Lautruphoej 1-3
2750 Ballerup
Danmark
Phone: [phone]
Fax: [phone]
NA Network Associates Oy
Mikonkatu 9, 5. krs.
00100 Helsinki
Finland
Phone: [phone]
Fax: [phone]