by Mary Hale

Created on: December 07, 2006   Last Updated: October 20, 2009

It seems like hardly a day goes by anymore that you don't hear someone mention a new computer virus that is on the rampage. There are hundreds of different anti-virus programs available, some free downloads from the Internet, others quite pricey that can be purchased on disks. They almost all have renewable subscriptions so that your virus definitions are up to date to protect your computer systems. With all this talk of viruses, it is not surprising that many people are asking just what is a computer virus.

Well, to put it in layman's terms, a computer virus is a computer program that attaches itself to another program on your system like a word processing program, for example. Every time you run the program that it has attached itself to, the virus also runs. It spreads to other programs, and does whatever damage it was created to do on your system. A true computer virus is not a free-standing program. It has to attach to another program on your system.

This is not true of all Malware programs - malicious programs that are designed to do some sort of damage to your system. Worms, for example, run independently of other programs. Unlike a true computer virus, they are freestanding programs. They work by scanning computers for specific security breaches in the system and then attacking the compromised computer through that breach. The worm then begins to look for other computers on the network that have the same security breach and infect them as well, rapidly compromising the entire computer network. They are typically designed to steal email addresses or take control of infected machines.

Another malicious program that is sometimes referred to as simply a computer virus is a Trojan horse. A computer becomes infected with a Trojan Horse when the user downloads a program that they think is useful, but in fact is the Trojan program instead. These programs create a serious identity theft problem because they are typically designed to steal passwords and other personal information stored on the infected machine.

There are also other Malware programs that you should be on the lookout for including spyware and adware. Spyware does just exactly what it sounds like it does. It spies on your activities on the infected computer. This usually involves watching your Internet browsing habits. Adware also spies on your browsing habits and then tries to target ads to your interests based on what sites you have visited. Though these programs seem harmless, they can rapidly eat into your system memory and drastically slow down your computer's response time.

There are many different signs and symptoms that your computer has become infected with a virus, worm, Trojan horse, or other malicious program. The machine will usually run much slower than normal because the virus is running in the background and using up valuable system memory. There will also be unusual messages and even the much feared blue screen of death that Windows users are so familiar with. If your computer starts to respond in strange ways, lock up, shut down unexpectedly, or simply is much more sluggish than usual it is a good idea to run a full system scan with an up to date anti-virus program to remove any infected files from the system. This will also prevent you from unknowingly spreading the infection to friend's and family's computers.

References:

How Stuff Works

http://www.howstuffworks.com/virus.htm

Wikipedia

http://en.wikipedia.org/wiki/Computer_virus

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