First the hacker sends a seemingly innocuous file via email to an unsuspecting person. But hidden within is an insidious program which can infiltrate the computer of the user who opened it. It gives them limited control of the machine. They can bide their time before doing anything, root around the system for passwords, find them and then email information to themselves. But certainly some source code has been taken and no one seems to be sure at this stage of exactly what the hackers have taken or whether they got what they were after.
Electronic logs show internal passwords being used to send source code outside the internal network.
One theory is that the hacker, rather than acting on behalf of a business rival, could just be motivated by pure mischief. If this was the case, the worst case scenario for Microsoft would be seeing the source code appear on a web site, or attacked in the future by viruses. The firm has stopped slightly short of saying so. It is too early to say, as the FBI investigation is just under way, with their principal lead the link to a Russian email account. If rivals have seen details of forthcoming Microsoft products this could threaten their dominant market share.