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Security from A to Z: Botnet

These armies of zombie PCs are used by cybercriminals for sending spam. Part of a series on hot security topics.

Natasha Lomas Mobile Phones Editor, CNET UK
Natasha Lomas is the Mobile Phones Editor for CNET UK, where she writes reviews, news and features. Previously she was Senior Reporter at Silicon.com, covering mobile technology in the business sphere. She's been covering tech online since 2005.
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Natasha Lomas
A botnet--also known as a "zombie network" or "zombie army"--is a collection of Internet-connected PCs that have been compromised by infection from malicious software.

That compromise means they can be controlled remotely by a malicious outsider, often without the PC owner's knowledge. Computers not protected by adequate antivirus and firewall software are at greatest risk of being corralled into a botnet.

Armies of zombie PCs are used by cybercriminals for sending spam or viruses or committing denial-of-service attacks. Capacity on botnets is rented out to criminal gangs or individuals for as little as $100 for a couple of hours by their creator--often a very commercially motivated virus writer.

A zombie army was used in a high profile distributed denial-of-service attack against Akamai Technologies this year, affecting the Web sites of some of its big-name tech clients.

Natasha Lomas reported for Silicon.com in London.