Detecting Malicious SMB Activity Using Bro

Attackers utilize the Server Message Block (SMB) protocol to blend in with network activity, often carrying out their objectives undetected. Post-compromise, attackers use file shares to move laterally, looking for sensitive or confidential data to exfiltrate out a network. Traditional methods for detecting such activity call for storing and analyzing large volumes of Windows event logs, or deploying a signature-based intrusion detection solution. For some organizations, processing and storing large amounts of Windows events may not be feasible. Pattern based intrusion detection solutions can be bypassed by malicious entities, potentially failing to detect malicious activity. Bro Network Security Monitor (Bro) provides an alternative solution allowing for rapid detection through custom scripts and log data. This paper introduces methods to detect malicious SMB activity using Bro.