ZyXEL Router Prestige 662HW-61 91-004-371001 Manual Do Utilizador

Prestige 662H/HW Series User’s Guide

Chapter 17 Anti-Virus Packet Scan

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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. 

The following table describes some of the common computer viruses. 

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.

Table 62   Common Computer Virus Types

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. 

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.