Suricata is an open source, multi-platform and totally free network intrusion prevention and detection engine developed by the Open Information Security Foundation (OISF) and its supporting vendors.
The IDS/IPS engine is multi-threaded
Suricata’s IDS/IPS engine is multi-threaded and has native IPv6 support. It's capable of loading existing Snort rules and signatures and supports the Barnyard and Barnyard2 tools.
It is highly scalable
You should try Suricata because its highly scalable, it recognizes most common protocols, and it can identify thousands of file types, check MD5 checksums, and extract files from archives.
Supports mainstream operating systems
Suricata is a cross-platform application that can be successfully used on GNU/Linux, BSD (FreeBSD and OpenBSD), Microsoft Windows and Mac OS X operating systems.
It’s distributed as a source archive
The software is only distributed as a source archive, which must be configure and compiled prior to installation. However, you can easily install it from the default software repositories of your Linux distribution. Both 32-bit and 64-bit hardware platforms are supported.
The best IDS and IPS software based on open source technologies
Suricata is without no doubt the best IDS (Intrusion Detection System) and IPS (Intrusion Prevention System) software ever built, powered only by open source technologies.