Microsoft has been participating in PRISM program (SIGAD US-984XN) since 2007.

https://en.wikipedia.org/wiki/PRISM

There are allegation that Microsoft changed Skype architecture (after buying Skype for $8.5 billion) to make wiretapping easier.

" In July last year, nine months after Microsoft bought Skype, the NSA boasted that a new capability had tripled the amount of Skype video calls being collected through Prism; "

https://www.theguardian.com/world/2013/jul/11/microsoft-nsa-...