Worms

Worms are programmes spreading automatically over network and they do not need a proper host programme for functioning. In many cases the worms, however, exploit the system they have infected, for instance by searching e-mail addresses in the system and by sending themselves to all of these addresses.

Traditionally, the worms have spread by exploiting incorrectly defined or vulnerable network services. At present, home computers with a permanent broadband network connection, without updating, with network services on with unpatched information security vulnerabilities, serve as an attractive basis for spreading of worms.

Worms are also spread by e-mail either in a attachment or in the message body. The activation of a worm in an attachment to an e-mail message usually requires the attachment to be opened, but in certain cases and in certain e-mail programmes the worm may be activated even in the preview. Once activated, the worm typically searches for e-mail addresses in the target computer and is thus spread forward.

In addition, certain worms use several mechanisms to spread. Those mechanisms can be spreading by e-mail, exploitation of vulnerable network services and open disk drives.