Computer viruses can wipe out or totally destroy a computer. They can be the worst program your computer has ever encountered. On the other hand, they can just be an annoyance. Computer viruses are put on computers without the owner's knowledge or permission. There are a variety of popular computer viruses that computer owners should be aware of.

Boot sector computer viruses:

A boot sector virus first became popular in the 1980's, when computer technology first began to take off. As its name states, a boot sector virus effects the boot sector of your computer - which is the bootable disk or hard drive. Some of the more damaging boot sector viruses that occurred in the past years included Disk Killer and Michelangelo.

Email viruses:

Email viruses use email to carry viruses from one computer to another. For example, if someone sends you an email message with an attachment that is infected by a virus, if you open up that attachment your computer will become infected. Some of the most malicious email viruses are smart enough to gather the email addresses of everyone in your email address book, and email themselves out to everyone. This, the virus can be spread extremely quickly. The best way to avoid getting an email virus is not to open email from email address that you don't recognize. Many email programs now come with virus scans of attachments before you even download them. Some email programs even separate large email files, most likely to be spam, into separate spam folders.

Companion viruses:

Companion viruses affect your computer's MS-DOS. Companion viruses have the ability to create malicious files that look exactly like valid files on your computer. For example, if you type in the name of a program that you want to use, and do not type the ".exe" extension to that program along with it, your computer's MS-DOS will think that you meant the file that comes frist in alphabetical order. Thus, your computer will then execute the virus instead of the program that you wanted to run. Luckily, running newer operating systems like Windows XP will prevent such viruses, as Windows XP does not use the MS-DOS prompt.

Trojan horse viruses:

Trojan horse viruses are actually a form of malware, but they are also considered viruses because of the damage that they can cause to your computer. Trojan horse virus is tricky. It can be something as simple as a desktop screensaver that you want to put on your computer. Only, when you install the screensaver with the virus, the Trojan horse actually goes in and lets hackers into your computer system. Hackers can take a look at any passwords, bank account, credit card, or other personal information you have on your PC. Trojan horse viruses can be so malicious that they can even erase your files without your consent.

If you want to stay safe from computer viruses such as the ones mentioned above, it is imperative that you purchase high-quality virus protection software as well as a firewall that will make it difficult for anyone or anything to access your computer.