If you’re reading this blog, you probably know that Bro can uncover indicators of compromise and discover adversary lateral movement by monitoring east-west traffic within the enterprise. But you may not know about one of the best sources of data for this purpose, the Bro server message block (SMB) logs. Bro’s SMB protocol analyzer has undergone several iterations, and it is now a built-in feature that many Bro users might have overlooked. If you are running Bro 2.5, all that is needed is to manually load the SMB policy.
SMB is used for many purposes. Most users of Windows networks rely on SMB every day when accessing files on network drives, and network administrators use the same protocol when they perform remote administration. Unfortunately the adversary, whether script kiddies or nation-state actors, also uses SMB! By the way, do you know whether SMBv1 is running on your network… and how can you be sure?
The video that accompanies this blog provides an introduction to the power of Corelight’s advanced filtering and the content contained in Bro’s SMB logs to monitor SMB usage for remote scheduled tasks and file access. If you use Bro to monitor SMB, please share tips here so others can benefit – if you don’t use Bro, would you like to learn how it transforms raw network traffic into comprehensive, organized logs? If you are interested in learning more detail about Bro’s ability to detect malicious activity hidden in SMB, this SANS paper is a great place to start.
I hope you enjoy this short introductory video. Good luck and good hunting!