For the first time criminal hackers may have succeeded in creating a network of 'zombie' cellphones, infected without the owners' knowledge with software that can be used to send spam or carry out cyber attacks. Botnets, as such networks are known, are usually made up of infected personal computers and are used to make money from spam or extortion. Millions of machines worldwide are secretly running botnet software and it has been estimated that one in four US personal computers is part of a botnet.
