A computer virus is software that can copy itself to other computers without the user being aware of it. Computer viruses can be dangerous because once a computer has been infected, the virus has virtually full control over the system.

So-called "spambots" are computers that have been infected by a virus that turned them into spam-sending machines. To prevent your computer becoming a spambot, a decent virus scan is vital. Moreover, many viruses spread via email; hence, an antispam solution that also scans for viruses provides you with the highest protection against infection.