1.3 What is a worm

Worms are similar to viruses but do not need a host file to replicate. Worms simply create exact copies of themselves and use communications between computers to spread. Worms share a common characteristic with trojans: they don't have the ability to infect a file, they will infect the system.

Worms may spread by email (using their own SMTP engine or a certain mail client, usually Microsoft Outlook or Outlook Express), by network shares, by instant messaging programs or by file sharing programs like KaZaA.

Virus Science