The FBI's new initiative, dubbed Operation Bot Roast, has uncovered one million compromised "zombie" PCs in the US. The US government will be contacting the owners of compromised machines, according to the agency. Botnets are the tools of choice for an enormous range of cybercrime, including distributed denial-of-service attacks to order, sending spam and running phishing scams.

Due to their distributed nature and increasing sophistication - many botnets use encryption, P2P technologies and other obfuscation techniques - the battle against botnet owners is an ongoing and costly process.

The FBI said in a statement that it has charged "numerous individuals with cyber crimes around the nation" following the operation. Only three men have been named so far: Robert Alan Soloway, accused of sending spam; James C Brewer, accused of infecting PCs worldwide; and Jason Michael Downey, accused of using botnets to disable other systems.