How Viruses Work

Viruses

A computer virus is defined as a self-replicating computer program that interferes with a computer's operating system or application
software. Computer programs that has been infected by a virus has been converted into a trojan horse. The program is expected to perform a useful function, but has the unintended side effect of viral code execution. Upon execution, the virus attempts to replicate and "attach" itself to another program. It is the unexpected and generally uncontrollable replication that makes viruses so dangerous.

 

How Computer Viruses Work

Basic viruses typically require unwary computer users to inadvertently share or send them. Some viruses that are more sophisticated, such as worms, can replicate and send themselves automatically to other computers by controlling other software programs, such as an e-mail
sharing application. If your system is infected, the virus may try to attach itself to every file in your system and spread each time you send a file or document to other users.

WHAT CAN VIRUSES DO?

Viruses used to play pranks or stop your computer from working, but now they not only do that, but they can compromise security in more insidious ways. These are the things that viruses can do.

•  Slow Down Email: Viruses that spread by email, such as Sobig, can generate so much email traffic that servers slow down or crash. Even if this doesn't happen, companies may react to the risk by shutting down servers anyway.

•  Steal Confidential Data: The Bugbear-D worm records the user's keystrokes, including passwords, and gives the virus writer access to them.

•  Use your computer to attack websites: MyDoom used infected computers to flood the SCO software company's website with data, making the site unusable (a denial of service --DOS-- attack).