London, July 12 (IANS/EFE): Microsoft cooperated closely with US intelligence agencies to facilitate the interception of private messages from its users, according to National Security Agency (NSA) documents revealed Thursday by the British daily The Guardian.

New information leaked by former CIA analyst Edward Snowden reveals how the Silicon Valley giant helped the NSA bypass the encryption system that protects conversations between users on the Outlook.com chat website.

According to the documents, the agency was already able to access e-mail messages sent via Outlook - which includes the Hotmail service - before the program encrypts them for secure sending.

Microsoft also worked this year with the FBI and the NSA to facilitate indiscriminate and mass access to information archived in the cloud-based SkyDrive service, which has some 250 million users.

In addition, the Skype video-chat service, a company Microsoft acquired in 2011 for about 6 billion euros ($7.86 billion at the current exchange rate), helped the US intelligence services intercept video and audio conversations, The Guardian said.

Snowden, who has been in limbo in the transit zone of Moscow's Sheremetyevo Airport since June 23, in early June leaked documents verifying the existence of the so-called Prism program, which allows intelligence agencies to access information that millions of users store in the servers of companies such as Google, Microsoft and Facebook.

The companies whose names appeared in Snowden's leaked documents denied that their programs contain backdoors to enable others to access the private information of their servers.

The newly revealed information, however, indicates that Microsoft provided technical solutions to the intelligence services to permit them to acquire direct access to conversations encrypted on Outlook.com.

A document dated Dec 26, 2012, that The Guardian says is an internal NSA communication says that Microsoft, working with the FBI, developed the monitoring ability to handle the problem, adding that the solutions were successfully tried and entered into operation Dec 12, 2012.

Another memo describes how the company headed by Steve Ballmer worked "for many months" with the secret services to give the Prism program access to SkyDrive without previous authorization.

That access capability means that analysts no longer have to make a special request of the SSO - a department within the NSA - to obtain such access, the document says.

After the first revelations about the Prism program emerged in June, Microsoft claimed it only cooperates with US intelligence services when it receives subpoenas and does not "participate in ... a broader voluntary national security program to gather customer data".