paper on the Bro network-intrusion detection system

[Vern Paxson <vern () ee lbl gov>]

"Bro: A System for Detecting Network Intruders in Real-Time", to appear
in the Proceedings of the 7th USENIX Security Symposium, 1998, is now
available from:

        ftp://ftp.ee.lbl.gov/papers/bro-usenix98.ps.Z

I've appended the abstract.

                Vern


Bro: A System for Detecting Network Intruders in Real-Time

Vern Paxson
Network Research Group
Lawrence Berkeley National Laboratory
vern () ee lbl gov

We describe Bro, a stand-alone system for detecting network intruders in
real-time by passively monitoring a network link over which the intruder's
traffic transits.  We give an overview of the system's design, which
emphasizes high-speed (FDDI-rate) monitoring, real-time notification, clear
separation between mechanism and policy, and extensibility.  To achieve
these ends, Bro is divided into an ``event engine'' that reduces a
kernel-filtered network traffic stream into a series of higher-level
events, and a ``policy script interpreter'' that interprets event handlers
written in a specialized language used to express a site's security
policy.  Event handlers can update state information, synthesize new
events, record information to disk, and generate real-time notifications
via syslog.  We also discuss a number of attacks that attempt to subvert
passive monitoring systems and defenses against these, and give particulars
of how Bro analyzes the four applications integrated into it so far:
Finger, FTP, Portmapper and Telnet.  The system is publicly available in
source code form.