Chapter 17 Anti-Virus Packet Scan; Overview; Types Of Computer Viruses; Signature-Based Virus Scan - ZyXEL Communications P-662HW-61 User Manual

This chapter introduces and shows you how to configure the anti-virus packet scan.

17.1 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.

17.1.1 Types of Computer Viruses

The following table describes some of the common computer viruses.

Table 62 Common Computer Virus Types

TYPE
File Infector
Boot Sector Virus
Macro Virus
E-mail Virus

17.2 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.

Chapter 17 Anti-Virus Packet Scan

C
Anti-Virus Packet Scan
DESCRIPTION
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.
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.
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.
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.
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