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.