Since the big security scares that surfaced last year, Google and other manufacturers have been updating their devices each month with a security update, to patch some of these vulnerabilities. Google just recently started pushing out their February 1st, 2016 patch this week, however it doesn't appear that many users have gotten the update just yet. Generally the update is pretty small, coming in at around 20MB or lower depending on the device. Google posted the factory images on Monday, for those that want to get the update right away, you're able to flash them and get the update right away. However that also means starting fresh with your data on your device. Luckily the OTA links have surfaced for most Nexus devices, allowing you to download the update and sideload the update to your Nexus device. A much easier process than flashing the factory image.
The February 1st, 2016 security update is also available for the BlackBerry Priv, but BlackBerry hasn't released any factory images for the Priv just yet, and likely won't. HTC should be rolling out their security updates in the next couple of weeks, especially with the unlocked HTC One A9 which is supposedly going to be getting updates within 15 days of it landing on Nexus devices. With the code already being in AOSP as of February 1st, we should be seeing custom ROM's updating with the latest security patch as well. Definitely important for those that use a Custom ROM on their device, as they always want to have the latest vulnerability patched up.
Below you will see Nexus devices that are getting the February Security Update, also listed is the old build and the new build. You will need to be on that old build for the OTA to work correctly, or you'll need to flash the entire factory image.
Nexus 5 - MMB29S to MMB29Q
Nexus 5X - MMB29P to MMB29Q
Nexus 6 - MMB29S to MMB29Q
Nexus 6P - MMB29P to MMB29Q
Nexus 7 2013 (WiFi) - MMB29O to MMB29Q
Nexus 7 2013 (HSPA) - MMB29O to MMB29Q
Nexus 9 (WiFi) - MMB29S to MMB29R
Nexus 9 (LTE) - MMB29S to MMB29R
Nexus 10 - LMY49F to LMY49G
Nexus Player - MMB29T to MMB29U