A court case in the US has revealed that Microsoft exercises the right to access any content on its email, chat areas, forums, and other communication facilities.

The tech giant has admitted to at least one case of snooping through a Hotmail inbox for information on a product leak.

The actions came to light in the proceedings of a legal case by US prosecutors against an ex-Microsoft employee, Alex Kibalko, a Russian native based in the company's Lebanon office accused to leaking files to an anonymous blogger.

The claims stem from a leak in 2012, when a few stolen lines of code from the Windows 8 operating system appeared in a screenshot on the blog site, some time before the software was actually released.

Microsoft set out to find the source of the leak, which included reading the emails of anyone involved on its services.

The search has been found to be legal as it falls within Microsoft's terms of service.

Everyone who signs up for a Hotmail account, now with Outlook, gives the company permission to access all information on its "Communication Services", which includes email, chat rooms, forums, and other services.

“Microsoft reserves the right to review materials posted to the Communication Services and to remove any materials in its sole discretion,” the Terms of Service say.

While the practice is legal, it has put Microsoft in a sticky place with regard to its stance on privacy, though it did claim that it took “extraordinary actions in this case”.

Microsoft has openly criticised a similar practice by its rival Google, which automatically scans users’ emails and browser history to serve them with targeted advertising.