ZyWALL 5/35/70 Series User’s Guide

CH A P T E R 14

Anti-Virus

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

14.1 Anti-Virus 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 82 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

Macro viruses or Macros are small programs that are created to perform repetitive

 

actions. Macros run automatically when a file to which they are attached is

 

opened. Macros spread more rapidly than other types of viruses as data files are

 

often shared on a network.

E-mail Virus

E-mail viruses are malicious programs that spread through e-mail.

 

 

Polyphormic Virus

A polymorphic virus (also known as a mutation virus) tries to evade detection by

 

changing a portion of its code structure after each execution or self replication.

 

This makes it harder for an anti-virus scanner to detect or intercept it.

 

A polymorphic virus can also belong to any of the virus types discussed above.

 

 

14.1.2 Computer Virus Infection and Prevention

The following describes a simple life cycle of a computer virus.

1A computer gets a copy of a virus from a source such as the Internet, e-mail, file sharing or any removable storage media. The virus is harmless until the execution of an infected program.

Chapter 14 Anti-Virus

254