# Malware

Malware (malicious software) refers to a variety of harmful programs that can infect a computer.

**Viruses** infect other software (a 'host program'). The virus spreads as the software is shared by users. Typically hey corrupt or modify files on the target computer.

**Worms** do not require a host program. They are standalone malware and they are able to spread on their own, without user interaction. The spread of worms can congest the network, but the 'payload' of a worm can cause additional harm to target devices.

**Trojan Horses** are harmful software that is disguised as legitimate software. They are spread through user interaction such as opening email attachments, or downloading a file from the Internet.