Google is keeping up with its promise to roll out monthly patches for Nexus devices, and it's really on the ball this time. The factory images for the February update are already available for download from the Google developer site. There are also some updated binaries for devices that need them.
The factory images are mostly build MMB29Q, but there are also others like MMB29U and MMB29R. They're all Android 6.0.1 and will raise the security patch level to February 1st, 2016. Google hasn't updated its security bulletin page with the specifics on this patch, but we'll let you know when they offer details.
To flash these images, you'll need to get ADB working on your computer and have an unlocked bootloader. If you don't meet those criteria, you can always wait for the OTA.
Google has posted the February security bulletin listing ten different issues that were fixed in this patch. Five of them were considered critical including a mediaserver remote exploit (reminiscent of Stagefright) and a Broadcom driver vulnerability. You can see the full notes here.