Snort is a free and open source network intrusion prevention system (NIPS) and network intrusion detection system (NIDS) created by Martin Roesch in 1998. Snort is now developed by Sourcefire, of which Roesch is the founder and CTO. In 2009, Snort entered InfoWorld's Open Source Hall of Fame as one of the "greatest open source software of all time".

You can find more document in here: https://www.snort.org/documents. This website provide everything you need when you work with Snort IDS.

I have Lab in my school about it, so i share for anyone want to see a sample video how to install, basic configure, basic test with installation file. It's make you easy to learn from basic to complicate (for example: when you integrate Snort with Iptables to become a soft-firewall).

A short clip i do Step-by-Step to install Snort on CenOS with basic test rule (Incoming ICMP, UDP). Download configure file here: http://bit.ly/1JgBXTy

Any question please comment below, i'll try my best to help you. Thank you!