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Network analysis with the Bro Network Security Monitor

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Article from ADMIN 24/2014

By Ronald McCarty

The Bro network analysis framework provides network security monitoring as well as more general network traffic analysis.

The Bro Network Security Monitor (Bro) is a network-based analysis framework. Bro's powerful analysis engine makes it adept at high-performance network monitoring, protocol analysis, and real-time application layer state information. This makes Bro a very good intrusion detection system (IDS) and network analysis framework. For this reason, analysis around IDS is one of the most popular uses for Bro.

What are some examples of analysis around IDS? Often, investigations concerning intrusions are not just about the identification of the event, which can often be accomplished with signatures, but about identification of the details of events to help information security professionals zone in on specific problems and solutions. Because logs can be compromised during an event, logging outside a compromised system is important. For example, while DHCP services are being compromised, protocol-level analysis can be key to understanding the event.

Bro was originally developed in 1994 by Vern Paxson and was named in reference to George Orwell's Big Brother from his novel Nineteen Eighty-Four . Unix history buffs and computer science majors may recognize Paxson as the original author of flex, the fast lexical analyzer. In this article, I cover the architecture, installation, and use of Bro. Finally, I look at a DHCP compromise example.

Bro Architecture

Bro, like many network tools with a Unix or Linux heritage, uses the libpcap package as part of its architecture. With libpcap support, Bro can run on various networks; the typical Bro architecture is shown in Figure 1.

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