Anti-Virus Information for Your Computer A computer virus is a program or piece of code that is loaded onto your computer without your knowledge and runs against your wishes. Most viruses can replicate themselves, are manmade, and are fairly easy to produce. Viruses are programmed to use memory, destroy hard drives, send emails, change keyboard key, or even transmit itself across networks and security systems. Once the infected program is run, the virus is transferred to your system's memory and may replicate itself further.
Macro viruses are currently the most commonly found viruses.
They infect files run by applications that use macro languages, like Microsoft Word or Excel. The virus looks like a macro in the file, and when the file is opened, the virus can execute commands understood by the application's macro language. Trojan or Worms are not technically viruses. A worm is a program that replicates itself, but does not necessarily infect other programs. These worms replicate themselves by e-mail, making use of any email programs such as Microsoft Outlook address books.