Microsoft is getting desperate to stop Android from taking over mobile devices.

Today, the company filed a patent infringement lawsuit against Barnes & Noble for using Android in its Nook device.

That's right -- not an Android phone maker, but a bookseller who happens to use Android in a way that most users don't even notice. In fact, unless you hack the Nook, you can't even see the Android interface or use any Android apps.

The move means that any company who uses Android in any capacity faces a legal threat from Microsoft.

Microsoft is probably on solid legal ground here. Android includes Linux at its core, and Microsoft established years ago that it thinks Linux infringes its patents. (That claim never been tested in court, but tons of Linux distributors have signed licensing deals anyway -- which boosts Microsoft's future claims.)

Last year Microsoft began trying to strike deals with Android smartphone makers. HTC signed a deal. Motorola didn't, and Microsoft sued.

But Motorola is a tech company and was able to sue Microsoft back by pointing to some of its own patents. That's not uncommon in patent cases, and usually paves the way for a settlement.

But apparently Microsoft will stop at nothing to stall Android adoption -- or at least earn some money from every single Android device that ships.