A 26 year-old computer security consultant from Los Angeles has admitted hijacking more than 250,000 PCs to rob users of money and identity information.

Federal prosecutors said that John Kenneth Schiefer deliberately infected the botnet of hijacked computers with spyware to steal personal data and serve victims with online advertising.

Schiefer now faces a prison sentence of up to 60 years and a $1.75m fine after agreeing to plead guilty to four felony charges of fraud and wiretapping.

Schiefer, who used the names 'acidstorm' and 'acid', is the first person to be accused under a Federal wiretapping law of operating a botnet.

Prosecutors claimed that Schiefer stole user names and passwords for PayPal's online payment service by intercepting electronic communications which he then used to make fraudulent purchases.

Schiefer was abetted by two minors, identified in the complaint only by their online screen names 'pr1me' and 'dynamic', according to investigators.

Together they hijacked more than 250,000 PCs installing malicious programs that allowed them to control the machines remotely, stealing user names and passwords that victims had saved in Internet Explorer.