According to the recently updated Microsoft Services Agreement—covering Xbox Live, and Xbox and Windows Games published by Microsoft—Microsoft can now disable pirated games from your computer. The clause can be found under section 7b, "Updates to the Services or Software, and Changes to These Terms." It reads:
"We may automatically check your version of the software and download software updates or configuration changes, including those that prevent you from accessing the Services, playing counterfeit games, or using unauthorized hardware peripheral devices. You may also be required to update the software to continue using the Services."
The clause was spotted by Alphr, and would suggest that Microsoft will disable pirated first-party games. The EULA also mentions "unauthorized hardware peripheral devices," which is a much more fuzzy description. Is it controllers that have been specifically hacked to enable an unfair advantage, or something much broader?
It's worth clarifying that this isn't a full hunt for all desktop software. Microsoft's Services Agreement doesn't cover Steam itself, or any other third-party desktop apps you have on your computer. It does, however, include all Xbox and Windows Games published by Microsoft.
Microsoft wants us to think they're newly recommitted to PC gaming—recently announcing Gears of War: Ultimate Edition and Halo Wars 2 as titles coming to Windows 10. I wouldn't be surprised to see—at the very least—all of their future games making use of this OS-level piracy scan.
Correction: Added a paragraph clarifying that this update doesn't apply to non-Microsoft services. The headline has been updated to reflect this fact.