|IDS||IDS (Intrusion Detection System) refers to a system that aims at detecting network attacks by analyzing traffic flow and looking for known malicious signatures, then matching them with a comprehensive database of exploits. This is refered to as rule-based IDS. More advanced and complex IDS systems might also use anomaly-based solutions for detecting not just known paterns but unknown attacks as well.
IDS are generally concerned with external attacks, and are only as effective as their databases/pattern recognition. They can prove a valuable tool in troubleshooting network problems and detecting/alerting about potential attacks.