Bro is a network analysis framework that is different from the typical IDS.
Adaptable - Bro's domain-specific scripting language enables site-specific monitoring policies.
Efficient - Bro targets high-performance networks and is used operationally at a variety of large sites.
Flexible - Bro is not restricted to any particular detection approach and does not rely on traditional signatures.
Forensics - Bro comprehensively logs what it sees and provides a high-level archive of a network's activity.
Commercially Supported - Broala provides enterprise-level support by the creators of Bro.
In-depth Analysis - Bro comes with analyzers for many protocols, enabling high-level semantic analysis at the application layer.
Highly Stateful - Bro keeps extensive application-layer state about the network it monitors.
Open Interfaces - Bro interfaces with other applications for real-time exchange of information.
Open Source - Bro comes with a BSD license, allowing for free use with virtually no restrictions.
While focusing on network security monitoring, Bro provides a comprehensive platform for more general network traffic analysis as well.