What the mainstream media often don't tell you--at least, in most radio and television newscasts and in the crucial headlines and opening paragraphs of newspaper articles-- is that many of these "viruses" are not viruses at all.
What Computer Viruses Really Are
The main reason the mainstream media always are in alarm over viruses is that they tend to call any malicious computer program a virus. In reality, there are at least eleven distinct types of malicious software, or malware, commonly affecting computers today. The most common of these are worms, Trojans, and spyware.
So, what's the difference between computer viruses and the other types of malware? The difference is that computer viruses are just about the only ones that regularly shut down computers and cause other obvious damage. The most common of the other kinds of malware--worms, Trojans, and spyware--are usually only detectable with a special scan.
The Real Danger of Computer Viruses
If the other types of malware are so unobtrusive that they can only be detected with a special scan, then what's to worry about? For starters, these programs are called malicious for a reason: they are designed to cause some kind of damage, if not to your computer, then to someone else's.
Worms are most famously used to damage, destroy, or disrupt other computer networks than the one on which the host computer is located. For instance, worms have been used by website owners to shut down rival websites by sending overwhelming numbers of requests to the computer that hosts that website. Worms have also been used to send out viruses to other computers, often without infecting the host machine--after all, what would it benefit the worm to shut down its host computer?
Trojans, in turn, are often used to insert worms and other malware on your computer, even if the Trojan itself does no damage.
But even if you don't care what happens to anyone else, you should still be concerned about one kind of malware: spyware, a kind of malware that, true to its name, collects data from your computer and sends it back to a remote host.
Most spyware is only interested in monitoring your internet usage so it can tell other programs, called adware, what advertising to popup on your computer. However, there are criminal spyware programs that steal financial data, or perform a thorough identity theft. Don't think you have personal or financial data on your computer? Some spyware programs contain a keylogger, which is a program that copies whatever you type, usually in order to snatch passwords. Even if you keep no financial information on your computer, if you ever buy anything over the web, the keylogger would allow its owner to buy stuff using the same information you typed in to buy stuff yourself.
Why Blame the Media?