Less than two weeks after Samsung announced the latest security patch for its main flagship models, AT&T started pushing the said update to its Galaxy Note 5 devices. Apart from additional security patches and fixes, the US carrier's support page claims that the update also brings some performance improvements. The update is exactly 43 MB in size and as it usually goes with these kinds of things, it may be a while before it's available for download on your device due to the staged rollout. In fact, AT&T claims the update even started rolling out yesterday, though there are currently no confirmed reports of any of their Galaxy Note 5-wielding customers receiving it on March 9th. The point is, be patient, it's definitely coming.
Naturally, if you aren't keen on waiting, you can also check for the security update manually by going into your Galaxy Note 5 Settings > General > About device > Software updates menu where you just have to hit the "Check for updates" option. After everything's said and done, or better said downloaded and installed, the "About device" page on your Galaxy Note 5 should say that the Android security patch level of your smartphone dates back to February 1st of 2016. Note how this Galaxy Note 5 update isn't a major OS upgrade as the software version will remain exactly where it is, at Android 5.1.1. Lollipop.
Regarding details on the update, AT&T was just as vague as Samsung was when it originally announced the patch in February. We do know that all of the security fixes from the somewhat less mysterious Google February update are included in its modified version of it, so exploits such as the one which bypasses the Android setup wizard definitely aren't an issue anymore, and the same goes for the now-former vulnerability which enabled code execution from something like an email or an MMS. Apart from that, Samsung did reveal that seven more security issues specific to Samsung devices are included in the patch, but no further details were provided. Given the sensitive nature of these updates, the kind of secrecy we are witnessing here is neither surprising nor unusual in the industry as most manufacturers will rather opt to keep their customers in the dark than to risk providing potential hackers with helpful information. Of course, pretty much all information can be helpful when it comes to hacking.