Viruses - How Viruses Work

To perform its function, a virus need only be able to replicate itself. Once a virus infects a computer—by e-mail, disk, or some other method—the program to which the virus is attached only has to be executed to trigger the virus into action. On top of mere replication, viruses may include a malicious payload, a mark that invites the user to perform an operation, such as opening an e-mail attachment. For example, the tag "I LOVE YOU" in the worm virus of the same name in 2000 constituted that virus's payload.

Viruses work in a variety of ways to disrupt a system, but the most common method was to simply overburden it by repeating the same messages over and over via rapid self-replications, eventually crashing the system. In addition, a computer virus may not take effect immediately. It can sit undetected in computer systems for months waiting for the right operation to trigger it into action. By that time, it may be quite difficult to retrace the steps of how a virus was lodged in a system to begin with.