McAfee VIRUSSCAN 5.1 User manual

McAfee VirusScan
User’s Guide
Version 5.1

COPYRIGHT
Copyright © 2000 Network Associates, Inc. and its Affiliated Companies. All Rights Reserved. No part
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to use one copy of the specified version of the Software and the accompanying documentation (the
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Issued July 2000/McAfee VirusScan v5.1

User’s Guide iii
Table of Contents
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .vii
What happened? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .vii
Why worry? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .vii
Where do viruses come from? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii
Virus prehistory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii
Viruses and the PC revolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
On the frontier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xii
Where next? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiv
How to protect yourself . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xv
Chapter 1. About VirusScan Software . . . . . . . . . . . . . . . . . . . . . . . . . . .17
Introducing VirusScan anti-virus software . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
How does VirusScan software work? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
What comes with VirusScan software? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
What’s new in this release? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
Chapter 2. Installing VirusScan Software . . . . . . . . . . . . . . . . . . . . . . . .31
Before you begin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
System requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
Other recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
Preparing to install VirusScan software . . . . . . . . . . . . . . . . . . . . . . . . .32
Installation options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32
Installation steps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32
Using the Emergency Disk Creation utility . . . . . . . . . . . . . . . . . . . . . . .43
Determining when you must restart your computer . . . . . . . . . . . . . . . .48
Testing your installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49
Modifying or removing your VirusScan installation . . . . . . . . . . . . . . . .50
Chapter 3. Removing Infections
From Your System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53
If you suspect you have a virus... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53
Deciding when to scan for viruses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56

Table of Contents
iv McAfee VirusScan
Recognizing when you don’t have a virus . . . . . . . . . . . . . . . . . . . . . . . . . . . .57
Understanding false detections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58
Responding to viruses or malicious software . . . . . . . . . . . . . . . . . . . . . . . . .59
Submitting a virus sample . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70
Using the SendVirus utility to submit a file sample . . . . . . . . . . . . . . . .71
Capturing boot sector, file-infecting, and macro viruses . . . . . . . . . . . .75
Chapter 4. Using the VShield Scanner . . . . . . . . . . . . . . . . . . . . . . . . . . .81
What does the VShield scanner do? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .81
Why use the VShield scanner? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .82
Browser and e-mail client support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83
Enabling or starting the VShield scanner . . . . . . . . . . . . . . . . . . . . . . . . . . . . .84
Using the VShield configuration wizard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .89
Setting VShield scanner properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .93
Using the VShield shortcut menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .149
Disabling or stopping the VShield scanner . . . . . . . . . . . . . . . . . . . . . . . . . .149
Tracking VShield software status information . . . . . . . . . . . . . . . . . . . . . . . .155
Chapter 5. Using the
VirusScan application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .157
What is the VirusScan application? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .157
Why use the VirusScan application? . . . . . . . . . . . . . . . . . . . . . . . . . . .158
Starting the VirusScan application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .159
Configuring the VirusScan Classic interface . . . . . . . . . . . . . . . . . . . . . . . . .164
Configuring the VirusScan Advanced interface . . . . . . . . . . . . . . . . . . . . . .169
Chapter 6. Creating and Configuring Scheduled Tasks . . . . . . . . . . . .187
What does VirusScan Console do? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .187
Why schedule scan operations? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .187
Starting the VirusScan Console . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .188
Using the Console window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .190
Working with default tasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .192
Working with the VShield task . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .194
Working with the AutoUpgrade and AutoUpdate tasks . . . . . . . . . . . .195
Creating new tasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .196
Enabling tasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .200

User’s Guide v
Table of Contents
Checking task status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .202
Configuring VirusScan application options . . . . . . . . . . . . . . . . . . . . . . . . . .204
Chapter 7. Using Specialized
Scanning Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .223
Scanning Microsoft Exchange and Outlook mail . . . . . . . . . . . . . . . . . . . . .223
When and why you should use the E-Mail Scan extension . . . . . . . . .223
Using the E-Mail Scan extension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .224
Configuring the E-Mail Scan extension . . . . . . . . . . . . . . . . . . . . . . . . .225
Scanning cc:Mail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .239
Using the ScreenScan utility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .239
Chapter 8. Using VirusScan Utilities . . . . . . . . . . . . . . . . . . . . . . . . . . .247
Understanding the VirusScan control panel . . . . . . . . . . . . . . . . . . . . . . . . .247
Opening the VirusScan control panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .247
Choosing VirusScan control panel options . . . . . . . . . . . . . . . . . . . . . . . . . .248
Using the Alert Manager Client Configuration utility . . . . . . . . . . . . . . . . . .251
VirusScan software as an Alert Manager client . . . . . . . . . . . . . . . . . . . . . . .252
Configuring the Alert Manager client utility . . . . . . . . . . . . . . . . . . . . . . . . . .252
Chapter 9. About Safe & Sound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .257
Using Safe & Sound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .258
Protected Volume Files (The Ultimate Backup Protection) . . . . . . . . .258
Why You Should Make Regular Backups With Safe & Sound . . . . . . .258
How Safe & Sound Creates Automatic Backups . . . . . . . . . . . . . . . . . .259
Defining Your Backup Strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .259
Where Will You Store the Backup Set? . . . . . . . . . . . . . . . . . . . . . . . . .260
What Files are Important to You? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .260
How Often Should You or Safe & Sound Make Backups? . . . . . . . . . .261
Chapter 10. About Quarantine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .263
Using Quarantine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .263
Reporting New Viruses or Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .264
Submitting Virus Information to Anti-Virus Emergency Response Team . .264
Appendix A. Default Vulnerable and Compressed File Extensions . .267

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vi McAfee VirusScan
Adding file name extensions for scanning . . . . . . . . . . . . . . . . . . . . . . . . . . .267
Current list of vulnerable file name extensions . . . . . . . . . . . . . . . . . . . . . . .268
Current list of compressed files scanned . . . . . . . . . . . . . . . . . . . . . . . . . . .272
Appendix B. Product Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .275
Updates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .275
How to Contact McAfee . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .275
Customer service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .276
Technical support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .276
Appendix C. Download Information (License ID #: VSF500R) . . . . . . .279
SecureCast™ (For Windows 95/98 Retail Version): . . . . . . . . . . . . . . . . . . .279
Internet Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .279
Appendix D. Using the SecureCast Service to Get New Data Files . .281
Introducing the SecureCast service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .281
Why should I update my data files? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .282
Which data files does the SecureCast service deliver? . . . . . . . . . . . .282
Installing the BackWeb client and SecureCast service . . . . . . . . . . . . . . . . .283
System requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .283
Troubleshooting the Enterprise SecureCast service . . . . . . . . . . . . . .293
Unsubscribing from the SecureCast service . . . . . . . . . . . . . . . . . . . . .293
Support resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293
SecureCast service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293
BackWeb client . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .294
Appendix E. Understanding iDAT Technology . . . . . . . . . . . . . . . . . . .295
Understanding incremental .DAT files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .295
How does iDAT updating work? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .296
What does McAfee VirusScan Software post each week? . . . . . . . . . .297
Best practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .298
Frequently asked questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .299
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .301

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.
Trackingdown thesource of resulting systemfreezes or crashescan 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
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 probablydoesn’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 associatedwith 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 fortheir 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
intheearly 1980s.Otherresearchers date theadvent of virus programs to1986,
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
Fora time,sophisticated descendants of this first boot-sectorvirus represented
the most serious virus threat to computer users. Variants ofboot 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 achance to do itswork before
your anti-virus software has a chance to run. Many McAfee VirusScan’s
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.
Thosesameviruseshavealsobenefittedfromseveralgenerationsofevolution,
andthereforeincorporatemuchmoresophisticatedinfectionandconcealment
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. Anearly 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 eachtime a userentered any standard DOScommand
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” requeststhat 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.

Preface
xii McAfee VirusScan
Macro viruses
By 1995or so,the viruswar hadcome tosomething ofa 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 attachfiles tomessages ensuredthat macroviruses would spreadvery
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 intoperhaps the most versatile and adaptable medium ever
invented for communication and commerce.
Because its potential seems so vast, the web has attracted theattention 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 paceof
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.
Somearespecial-purposeminiatureapplications,or“applets,”written inJava,
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
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 VirusScan’s 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 VirusScan’s software to detect and
remove viruses can getquickly outdated. Ifyou have not updated the files that
originally came with your software, you could risk infection from newly
emerging viruses. McAfee VirusScan’s Software 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 VirusScan’s 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 adequatetraining
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 VirusScan Software 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

1
User’s Guide 17
1About VirusScan Software
The VirusScan Central is your main entry point in using all of the available
components of McAfee VirusScan. This home screen provides relevant
information such as the last time a virus scan was performed on your
computer; what VShield settings are enabled or disabled (for more
information see Using VShield Scanner; and available DAT information and
when it was created.
Through this user-friendly interface, you can access the main functions of
McAfee VirusScan. Click the appropriate buttons as displayed to start
performing a particular task within McAfee VirusScan (e.g., Scan, Schedule,
Quarantine, etc).
You can also click the Update button to start searching and downloading any
availableupdatestoMcAfee VirusScaninstalledon yourcomputer.Make sure
that you are connected to the Internet prior to using this feature. For more
information and step-by-step instructions, click the Help icon on the upper
right-hand corner of the window. To view available options in customizing
how you want McAfee VirusScan components to work on your PC, click the
Options button.
Introducing VirusScan anti-virus software
Eighty percent of the Fortune 100—and more than 50 million users
worldwide—choose VirusScan anti-virus software to protect their computers
from the staggering range of viruses and other malicious agents that has
emerged in the last decade to invade corporate networks and cause havoc for
business users. They do so because VirusScan software offers the most
comprehensive desktop anti-virus security solution available, with features
that spot viruses, block hostile ActiveX and Java objects, identify dangerous
websites, stop infectious e-mail messages—and even root out “zombie” agents
that assist in large-scale denial-of-service attacks from across the Internet.
They do so also because they recognize how much value McAfee VirusScan
anti-virus research and development brings to their fight to maintain network
integrity and service levels, ensure data security, and reduce ownership costs.
With more than 50,000 viruses and malicious agents now in circulation, the
stakes in this battle have risen considerably. Viruses and worms now have
capabilities that can cost an enterprise real money, not just in terms of lost
productivity and cleanup costs, but in direct bottom-line reductions in
revenue, as more businesses move into e-commerce and online sales, and as
virus attacks proliferate.

About VirusScan Software
18 McAfee VirusScan
VirusScan software first honed its technological edge as one of a handful of
pioneering utilities developed to combat the earliest virus epidemics of the
personal computer age. It has developed considerably in the intervening years
to keep pace with each new subterfuge that virus writers have unleashed. As
one of the first Internet-aware anti-virus applications, it maintains its value
today as an indispensable business utility for the new electronic economy.
Now, with this release, VirusScan software adds a whole new level of
manageability and integration with other McAfee VirusScan’s anti-virus tools.
Architectural improvements mean that each VirusScan component meshes
closely with the others, sharing data and resources for better application
response and fewer demands on your system. Full support for Network
Associates ePolicy Orchestrator management software means that network
administrators can handle the details of component and task configuration,
leaving you free to concentrate on your own work. A new incremental
updating technology, meanwhile, means speedier and less
bandwidth-intensive virus definition and scan engine downloads—now the
protection you need to deal with the blindingly quick distribution rates of
new-generation viruses can arrive faster than ever before.
The new release also adds multiplatform support for Windows 95, Windows
98, Windows ME, Windows NT Workstation v4.0, and Windows 2000
Professional, all in a single package with a single installer, but optimized to
take advantage of the benefits each platform offers. Windows NT Workstation
v4.0 and Windows 2000 Professional users, for example, can run VirusScan
software with differing security levels that provide a range of enforcement
options for system administrators. That way, corporate anti-virus policy
implementation can vary from the relatively casual—where an administrator
might lock down a few critical settings, for example—to the very strict, with
predefined settings that users cannot change or disable at all.
At thesame time,as thecornerstone product in theMcAfee VirusScan’sActive
Virus Defense and Total Virus Defense security suites, VirusScan software
retains the same core features that have made it the utility of choice for the
corporate desktop. These include a virus detection rate second to none,
powerful heuristic capabilities, Trojan horse program detection and removal,
rapid- response updating with weekly virus definition (.DAT) file releases,
daily beta .DAT releases, and EXTRA.DAT file support in crisis or outbreak
situations. Because more than 300 new viruses or malicious software agents
appear each month McAfee VirusScan Software backs its software with a
worldwide reach and 24-hour “follow the sun” coverage from its Anti-Virus
Emergency Response Team (AVERT).

User’s Guide 19
About VirusScan Software
Even with the rise of viruses and worms that use e-mail to spread, that flood
e-mail servers, or that infect groupware products and file servers directly, the
individual desktop remains the single largest source of infections, and is often
the most vulnerable point of entry. VirusScan software acts as a tireless
desktop sentry, guarding your system against more venerable virus threats
and against the latest threats that lurk on websites, often without the site
owner’s knowledge, or spread via e-mail, whether solicited or not.
In this environment, taking precautions to protect yourself from malicious
software is no longer a luxury, but a necessity. Consider the extent to which
you rely on the data on your computer and the time, trouble and money it
would take to replace that data if it became corrupted or unusable because of
a virus infection. Corporate anti-virus cleanup costs, by some estimates,
topped $16 billion in 1999 alone. Balance the probability of infection—and
your company’s share of the resulting costs—against the time and effort it
takes to put a few common sense security measures in place, and you can
quickly see the utility in protecting yourself.
Even if your own data is relatively unimportant to you, neglecting to guard
against viruses might mean that your computer could play unwitting host to
a virus that could spread to computers that your co-workers and colleagues
use. Checking your hard disk periodically with VirusScan software
significantly reduces your system’s vulnerability to infection and keeps you
from losing time, money and data unnecessarily.
How does VirusScan software work?
VirusScan software combines the anti-virus industry’s most capable scan
engine with top-notch interface enhancements that give you complete access
to that engine’s power. The VirusScan graphical user interface unifies its
specialized program components, but without sacrificing the flexibility you
need to fit the software into your computing environment. The scan engine,
meanwhile, combines the best features of technologies that McAfee and
McAfee VirusScan researchers developed independently for more than a
decade.
Fast, accurate virus detection
The foundation for that combination is the unique development environment
that McAfee VirusScan researchers constructed for the engine. That
environment includes Virtran, a specialized programming language with a
structure and “vocabulary” optimized for the particular requirements that
virus detection and removal impose. Using specific library functions from this
language, for instance, virus researchers can pinpoint those sections within a

About VirusScan Software
20 McAfee VirusScan
file, a boot sector, or a master boot record that viruses tend to infect, either
because they can hide within them, or because they can hijack their execution
routines. This way, the scanner avoids having to examine the entire file for
virus code; it caninstead sample the file at well defined points to look for virus
code signatures that indicate an infection.
Thedevelopmentenvironment brings asmuchspeed to.DATfile construction
as it does to scan engine routines. The environment provides tools researchers
can use to write “generic” definitions that identify entire virus families, and
that can easily detect the tens or hundreds of variants that make up the bulk of
new virus sightings. Continual refinements to this technique have moved
most of the hand-tooled virus definitions that used to reside in .DAT file
updates directly into the scan engine as bundles of generic routines.
Researchers can even employ a Virtran architectural feature to plug in new
engine “verbs” that, when combined with existing engine functions, can add
functionality needed to deal with new infection techniques, new variants, or
other problems that emerging viruses now pose.
This results in blazingly quick enhancements the engine’s detection
capabilities and removes the need for continuous updates that target virus
variants.
Encrypted polymorphic virus detection
Along with generic virus variant detection, the scan engine now incorporates
a generic decryption engine, a set of routines that enables VirusScan software
to track viruses that try to conceal themselves by encrypting and mutating
their code signatures. These “polymorphic” viruses are notoriously difficult to
detect, since they change their code signature each time they replicate.
This meant that the simple pattern-matching method that earlier scan engine
incarnations used to find many viruses simply no longer worked, since no
constant sequence of bytes existed to detect. To respond to this threat, McAfee
VirusScan researchers developed the PolyScan Decryption Engine, which
locates and analyzes the algorithm that these types of viruses use to encrypt
and decrypt themselves. It then runs this code through its paces in an
emulated virtual machine in order to understand how the viruses mutate
themselves. Once it does so, the engine can spot the “undisguised” nature of
these viruses, and thereby detect them reliably no matter how they try to hide
themselves.