PSAD rules for LCE and Firewall Monitoring in General
Tenable's research group released a Log Correlation Engine (LCE) log parser library for events generated by the Port Scan Anomaly Detector (PSAD) tool. The LCE PRM library is available here for download. PSAD considers logs from the Netfilter firewall and alerts when port scans occur. It also has the ability to react to the scan by adding "block" rules to the firewall.
Adding the PRM to the Log Correlation Engine
Using wget, download the PSAD PRM library, as well as the latest copy of the prm_map.prm file. This is a list of all PRM event IDs and is required by TASL scripts such as the Never Before Seen script. If users have also deployed the portscan_spike.tasl script, it has been updated to accept port scan detects from PSAD.
Firewall Monitoring and Cipherdyne
Michael Rash runs the Cipherdyne web site which hosts his blog and several useful tools relating to iptables. He also has an upcoming book titled "Linux Firewalls: Attack Detection and Response". I've had the chance to review an early copy and think it will be very useful for organizations that run Linux firewalls.
A general theme in Michael's work is that firewall log data should be considered for security monitoring and incident response. Too often, I encounter organizations that consider a firewall as purely an access control enforcement device and not something that can produce rich logs.
The firewall PRMs written for the Log Correlation Engine not only process accept and deny events, but also proprietary events such as port scan detection, spoofing events, attacks on the firewall and perhaps the most import type of log, firewall configuration changes.
In the absence of netflow or direct network sniffing, a firewall's "accept" logs could be the only evidence of a network connection. Many of the TASL scripts written for the LCE will process firewall logs just as readily as a netflow or sniffed session.