(Snort is a powerful and lightweight network intrusion/intrusion detection system. It has real-time data traffic analysis, can do protocol analysis, and find/match content. It can detect a variety of different attack methods and give real-time alarm to the attack. Describe it in one sentence "always imitated, never surpassed" This article introduces Ruan's construction of snort under the FreeBSD platform, which is worth learning.
Lightweight Detection System (IDS) based on FreeBSD Snort.pdf)