Practically everyone with a computer has heard of computer viruses, but not everyone knows exactly what they are or how viruses can affect their computer. A virus is a small, self-replicating program that invades your system through an e-mail attachment, download, or Web site. People create viruses or various reasons, ranging from mild pranks to malicious destruction.As a result, the effects of a virus can vary from moderately annoying to absolutely crippling. The Wazzu virus, for example, attaches itself to Microsoft Word documents and inserts the nonsense word “?wazzu?” in the document and rearranges random strings of words. A virus such as this one is definitely annoying, but not necessarily catastrophic.
Some viruses can be much more serious, however, threatening to destroy data or even erase your entire hard drive. One such virus spread by e-mail, Worm.ExploreZip, takes control of the infected computer’s e-mail system and automatically responds to all incoming mail messages. It also sends destructive e-mail attachments that can erase certain types of files.
Viruses can be harmful, but it’s also important to understand the role you play in propagating them. Viruses generally do not invade a computer without user action. In other words, you set the virus loose on your own computer by opening infected programs or files. If you take certain precautions, such as not opening email attachments from unknown sources and running antivirus software, you can minimize the risk of infecting your own computer.
Types of Viruses
By familiarizing yourself with the types of viruses that exist, you’ll be better able to prevent them.
Program viruses attach themselves to executable files such as .exe files. Each time you run the program, the virus duplicates itself and attaches to other programs. Sharing programs with other computers, either by disk or on a network, spreads these types of viruses. You are also at risk for this type of virus when you download applications from the Internet.
Macro viruses are contained in the macro commands for programs such as Microsoft Word and Excel. Perhaps the most prevalent type of virus, they attach themselves to files (as opposed to programs) and are some of the hardest viruses to detect. You can learn more about the special dangers posed by these viruses in How Are Macro Viruses Different from Others?
Boot sector viruses infect particular files on your hard drive that execute when you boot your computer. When you boot from the infected disk, the boot sector virus attaches itself to the boot files on your hard drive.
Trojan horses aren’t viruses by definition because they don’t replicate themselves. They do, however, possess the same potential to damage your hard drive if they go undetected. They typically arrive in an e-mail with a vague subject line or a promise of entertainment. When let loose, the Trojan horse — much like its namesake in Greek mythology — introduces a slew of unwanted attackers that can wreak havoc on your hard drive.
