Chapter 1. Introduction; Computer Viruses And Malware - KAPERSKY ANTI-VIRUS 5.5 - FOR LINUX-FREEBSD WORKSTATION AND FILE SERVER Administrator's Manual

CHAPTER 1. INTRODUCTION

The constant growth in the number of computer users and new the possibilities
of data exchange between them via e-mail or internet result in the increased
threat of virus infections and data corruption or theft by malicious computer
programs.
Among the sources of malware penetrating users' computers the most
dangerous are:
Internet
Global information network is the main source of distribution of all types of
malware. As a rule, viruses and other malicious programs are be located
on popular internet websites disguising themselves as useful software or
freeware. Malware can be located within numerous scripts that automati-
cally run when a website is loaded in the user's browser.
E-mail messages
E-mail messages delivered to the user's mailbox and stored in the e-mail
databases may contain viruses. Malware can be located either in the at-
tachments to messages or in the body of a message. As a rule, infected
e-mail messages contain viruses or mail worms. When you open an e-
mail message or save an attached file to your hard drive, you may infect
data stored in your computer.
Software vulnerabilities
In most cases hackers' attacks are attempted using "software holes".
Such vulnerabilities allow hackers to obtain remote access to your com-
puter and, therefore, to your data, your LAN resources and other sources
of information.
In the Unix-based systems viruses are far less common compared, for example,
to the Windows Operating System due to the peculiarities of the two platforms.
However, this does not mean that Unix users encounter no threat. Provided
below is a detailed description of malware types.

1.1. Computer viruses and malware

In order to be aware of the potential threats to your computer, it is helpful to know
what the types of malicious software ("malware") are and how they work. In
general, malicious programs fall into one of the following three categories: