Don't Knock Bro

Today's defenders often focus detections on host-level tools and techniques thereby requiring host logging setup and management. However, network-level techniques may provide an alternative without host changes. The Bro Network Security Monitor (NSM) tool allows today's defenders to focus detection techniques at the network-level. An old method for controlling a concealed backdoor on a system using a defined sequence of packets to various ports is known as port-knocking. Unsurprisingly, old methods still offer value and malware, defenders, and attackers still use port-knocking. Current port-knocking detection relies on traffic data mining techniques that only exist in academia writing without any applicable tools. Since Bro is a network-level tool, it should be possible to adapt these data mining techniques to detect port-knocking within Bro. This research will document the process of creating and confirming a port-knocking network-level detection with Bro that will provide an immediate and accessible detection technique for organizations.