Microsoft security researchers estimate more than 2.2 million computers in the US are part of botnets, and may be used by criminals to send out spam, phishing e-mails and launch attacks on websites. Cliff Evans, head of security and identity at Microsoft UK, recommends users to activate automatic updates, make sure all software they use is regularly patched, use anti-virus software and run a firewall to prevent infections.
More than 2.2 million US PCs were found to be part of botnets, networks of hijacked home computers, in the first six months of 2010, it said.
Compiled by Microsoft, the research revealed that Brazil had the second highest level of infections at 550,000.
Infections were highest in South Korea where 14.6 out of every 1000 machines were found to be enrolled in botnets.
The 240-page Microsoft report took an in-depth look at botnets which, said Cliff Evans, head of security and identity at Microsoft UK, now sat at the centre of many cybercrime operations.