If you own a computer or use one on a regular basis, you've undoubtedly heard a lot about computer viruses. As ubiquitous as the concept of the computer virus is, there are a lot of misconceptions about them. In order to avoid the problems that viruses can cause, it helps to know a little about them. The following information will help you get a basic feel for what a computer virus is.
A Computer Virus is a program that can infect a computer and make copies of itself without the permission of the user. Viruses do their damage by attaching themselves to legitimate files within a computer. They most commonly piggyback on executable files like those with .EXE and .COM extensions. When you run an infected program, the virus also runs and does its programmed function.
The most insidious thing about well-designed computer viruses is that they usually don't make any noticeable changes to the files they infect. For instance, the "last modified" date and time on an infected file won't usually change when a virus attaches itself to it. Similarly, the size of an infected file won't change when a virus gets on board; host files aren't usually damaged or corrupted, either. In other words, these executable files look and appear to be completely fine; unfortunately, they harbor dirty secrets that can wreak serious havoc on your computer.
How Viruses Spread:
Human viruses are passed from person to person through sneezes, coughs and other occurrences. Germs hitch rides in phlegm and mucus; when those things land on another person, germs have a field day and the person often becomes ill. Computer viruses are also spread by well-meaning humans. If someone wants a copy of another person's spreadsheet program, for instance, they may copy it to a disk then install it on their PC. The virus is copied along with everything else, infecting the new computer in one fell swoop.
Viruses are most commonly spread via email in the form of attachments. They can be passed along through the Internet and over computer networks, too. In other words, they have plenty of opportunities to get spread around.
Avoiding Computer Viruses:
There's no surefire way to completely avoid all computer viruses. However, a good free anti-virus program such as Avast! Free AntiVirus or AVG AntiVirus Free can work wonders. Such programs are loaded with the definitions, or characteristics, of common viruses. Of course, some especially well-designed viruses change their code with each new infection. In addition to using an antivirus program, then, you should never open or run any unfamiliar file or program - especially if you receive it via email from someone you don't know. There's no way to eliminate the threat of viruses altogether, but a little common sense goes a long way.