Internet worms

Worms are programs that create copies of themselves and spread via internet connections.

Worms differ from computer viruses because they can propagate themselves, rather than using a carrier program or fi le. They simply create exact copies of themselves and use communication between computers to spread.

Internet worms can travel between connected computers by exploiting security “holes” in the computer’s operating system. The Blaster worm, for example, takes advantage of a weakness in the Remote Procedure Call service that runs on unpatched Windows NT, 2000 and XP computers and uses it to send a copy of itself to another computer.

Many viruses, such as MyDoom or Bagle, now behave like worms and use email to forward themselves.

A worm can have malicious effects. For example, it may use affected computers to deluge websites with requests or data, causing them to crash (a “denial-of-service” attack). Alternatively, it can encrypt a user’s fi les and make them unusable. In either case, companies can be blackmailed.

Many worms open a “back door” on the computer, allowing hackers to take control of it. Such computers can then be used to send spam mail (see Zombie).

Quite apart from such effects, the network traffi c generated by a fast-spreading worm can slow down communications. The Blaster worm, for example, creates a lot of traffi c on the internet as it spreads, slowing down communications or causing computers to crash. Later it uses the affected computer to bombard a Microsoft website with data, with the aim of making it inaccessible.

Microsoft (and other operating system vendors) issue patches to fi x security loopholes in their software. You should update your computer regularly by visiting the vendor’s website.