THE DAYS WHEN VIRUSES were the greatest threat to computers

are long gone. Today, a virus is just one of many categories of malicious

software, or malware, that can wreak havoc on computer systems and networks.

Deluged with such a huge assortment of threats to their systems and

often unable to distinguish one type of threat from another, individual computer

users and businesses have had to defend themselves by purchasing

all kinds of security software. Section E explains how you can use security

software to combat malicious software that threatens your computer.

Security software basics

What is security software? Security software is designed to protect

computers from various forms of destructive software and unauthorized

intrusions. One of the first security software offerings was created by Dr.

Peter Tippett, an emergency room physician who took a page from conventional

medicine and applied it to computer viruses. The security software

developed by Dr. Tippett was sold to Symantec Corporation in 1992 and

incorporated into the popular Norton AntiVirus software.

Security software can be classified into various types: antivirus, anti-spyware,

anti-spam, and firewalls. Each type focuses on a specific security

threat.

What are malware threats? The terms malicious software and

malware refer to any computer program designed to surreptitiously enter a

computer, gain unauthorized access to data, or disrupt normal processing

operations. Malware includes viruses, worms, Trojans, bots, and spyware.

Malware is created and unleashed by individuals referred to as hackers,

crackers, black hats, or cybercriminals. The motivation behind malware

is varied. Some malware is intended to be a relatively harmless prank or

mildly annoying vandalism. Other malware is created to distribute political

messages or to disrupt operations at specific companies. In an increasing

number of cases, the motivation is monetary gain. Malware designed

for identity theft or extortion has become a very real threat to individuals

and corporations. Organized crime bosses, drug traffickers, and terrorists

are joining forces with cybercriminals to increase the sophistication of their

activities (Figure 3-44).

Emerging security threats often combine and refine old exploits,

blurring the lines between viruses, worms, and other kinds of malware.

For example, a Trojan horse might carry a bot that turns

a victim’s computer into a distribution point for a mass-mailing

worm. Security experts use the term blended threat to describe

malware that combines more than one type of malicious program.

Although the nuances of blended threats are beyond the scope

of this chapter, it is important to understand the threats posed by

malware if you hope to avoid identity theft and other inconvenient

computing incidents.

Figure 3-44

Security breaches were once little

more than pranks, but today’s

threats from organized crime and

terrorists are serious concerns for

Individuals as well as for corporations

and governments

What is a virus? A computer virus is a set of program instructions that

attaches itself to a file, reproduces itself, and spreads to other files. A common

misconception is that viruses spread themselves from one computer

to another. They don’t. Viruses can replicate themselves only on the host

computer. A key characteristic of viruses is their ability to lurk in a computer

for days or months, quietly replicating themselves. While this replication

takes place, you might not even know that your computer has contracted

a virus; therefore, it is easy to in advertently spread infected files to other

people’s computers.