Botnets grow by 50 per cent

Twelve million new IP addresses have been taken control of by cybercriminals, leading to a growth in the number of 'bots' worldwide.

A bot is a computer that has been taken over by hackers and is used for criminal ends such as sending large amounts of spam or spreading malware. A network of these computers is known as a botnet.

The spike in the number of bots was outlined in McAfee's Threat Report for the first quarter of 2009.

"The massive expansion of these botnets provides cybercriminals with the infrastructure they need to flood the web with malware," said Jeff Green, senior vice president of McAfee's Avert Labs.

Some 18 per cent of the bots are in the United States, said McAfee, and have enabled spammers to flood the web with unsolicited emails close to the level seen before the notorious McColo web-hosting service was shut down in November 2008.

McAfee's report also showed new activity by worms that target social networks – the Koobface worm, which pestered Facebook members last year, has developed more than 800 new variants, the security firm said.