Computer Viruses : A SearchMeSilly Guide

• Viruses - A program which attaches itself to a document or another program with the intention of replicating itself and/or causing harm.
   
• E-mail viruses – This type of virus replicates via e-mail. The malicious code is usually present within an attachment and lays dorment until activated by the user (for example, if the file is double clicked). The virus then automatically mails itself to contacts of the user.
   
• Worms – A stand-alone program that exploits networks environments and security holes to replicate itself. It scans the network for a security hole which allows it to copy itself to another computer where it begins the process again. Worms can spread quickly and have the capacity to slow down, or even crash a network.
   
• Trojan horses - A computer program diguised as one thing, but once run, can do irrepricable damage such as deleting your hard disk. Commonly however, it creates a back door which gives others unauthorised access and controll of the system. Unlike other forms, they have no way to replicate automatically.