Sprint is rolling out an over-the-air update to customers who own a Galaxy Note II that applies a security patch or two from Google. What vulnerability this update addresses isn't detailed, but it's the first OTA Sprint has sent out since the big KitKat update last May.
Once the goods arrive, they will leave your phone Note II running software version L900VPUCNK2. There's nothing else on the changelog, so don't go digging around looking for anything exciting.
You can check for the update manually, but do so knowing that you're making your phone just a little bit safer. Don't do it because it's fun. The only exciting thing here is watching the version number go up, which I will admit, does provide somewhat of a thrill all its own.