BBC News Online: Business

Hackers hit Microsoft

The attack was discovered by security staff on Wednesday and was being investigated by the company and the US Federal Bureau of Investigation.

The hackers were thought to have had access to source codes behind Microsoft's software for three months and could have stolen blueprints of the firm's Windows and Office products.

"Microsoft is moving aggressively to isolate the problem and to secure our corporate network," company spokesman Rick Miller said.

"We are confident that the integrity of our source code remains secure.

"We're still looking into it. We're still trying to figure out how it happened," said Mr Miller.

"This is a deplorable act of industrial espionage and we will work to protect our intellectual property," he said.

Russian account

He said there was no evidence that any source code for Windows or other commercial software made by Microsoft had been modified or corrupted since the computer system had been broken into.

The Wall Street Journal said security employees had discovered that passwords used to transfer the source code behind Microsoft's software were being sent from the company's computer network in Redmond, Washington, to an e-mail account in St. Petersburg, Russia.

Microsoft said it was making sure hackers could not use the stolen source code to change commercial software used by businesses, governments and consumers.