ZyXEL Communications Prestige 662HW Series, User Manual

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Prestige 662HW Series User’s Guide
Anti-Virus Packet Scan 14-1
Chapter 14
Anti-Virus Packet Scan
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This chapter introduces and shows you how to configure the anti-virus packet scan.
14.1 Overview
A computer virus is a small program designed to corrupt and/or alter the operation of other legitimate
programs. A worm is a self-replicating virus that resides in active memory and duplicates itself. The
effect of a virus attack varies from doing so little damage that you are unaware your computer is
infected to wiping out the entire contents of a hard drive to rendering your computer inoperable.
14.1.1 Types of Computer Viruses
The following table describes some of the common computer viruses.
Table 14-1 Common Computer Virus Types
TYPE DESCRIPTION
File Infector This is a small program that embeds itself in a legitimate program. A file infector is able to
copy and attach itself to other programs that are executed on an infected computer.
Boot Sector Virus This type of virus infects the area of a hard drive that a computer reads and executes during
startup. The virus causes computer crashes and to some extend renders the infected
computer inoperable.
Macro Virus Macros are small programs that are created to perform repetitive actions. Macros run
automatically when a file to which they are attached is opened. Macro viruses spread more
rapidly than other types of viruses as data files are often shared on a network.
Trojan Horse A Trojan horse is a harmful program that s hidden inside apparently harmless programs or
data.
Worm A worm is a program that is designed to copy itself from one computer to another on a
network. A worm’s rapid replication consumes system resources thus slowing or stopping
other tasks.
E-mail virus E-mail viruses are malicious programs that spread through e-mail. These can infect your
computer even if you do not read the e-mail messages.
14.2 Signature-Based Virus Scan
The “signature-based” approach is the most common way to detect the presence of viruses. Signature-
based anti-virus scanning consists of two key components: a pattern file that contains the signatures
for known viruses and a scanning engine.
Signatures are byte patterns that are unique to a particular virus. These signatures are stored in a
pattern file. The scanning engine compares the files with the signatures in the pattern file.
For maximum protection, you must keep the pattern file up-to-date.
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