Originally written by Vern Paxson, Bro is an open source Unix based network monitoring framework. Often compared to a Network intrusion detection systems (NIDS), Bro can be used to build a NIDS but is much more. Bro can also be used for collecting network measurements, conducting forensic investigations, traffic baselining and more. Bro has been compared to tcpdump, Snort, netflow, and Perl (or any other scripting language) all in one. It is released under the BSD license.