Microsoft source code may have been stolen

Hackers gained entry to Microsoft's network for at least 12 days last month, leading to speculation that source code of still-unreleased products may have been stolen and sent to an email address in Russia.

Microsoft called in the FBI last week after discovering internal passwords being remotely sent to an email account in St Petersburg.

Microsoft's corporate security officer told the New York Times that at least one of the breaches could have happened through an employee's home PC connected to the company network.

The tool used by the hacker is the QAZ Trojan horse, which is delivered by email and opens a back door, giving the intruder remote control over the infected computer, according to a source used by the Wall Street Journal, which first broke the story last week.

Employee passwords could then have been collected and sent to the Russian email address, giving the hacker access to parts of Microsoft's company network.

"Microsoft security became aware of the illegal activity shortly after it first occurred, and tracked the hacker's attempts to expand his unauthorised access to our network over a 12-day period from 14 October to 25 October," said a statement issued by the company on Sunday.

Microsoft later admitted that the hacker "may have viewed the source code for a single future product under development".