An intrusion detection system (IDS) is an important network security tool that monitors network traffic for suspicious activity. If it finds something unusual or alarming, such as a malware attack, the IDS alerts a network administrator. Some intrusion detection systems even take action against threats by blocking a suspicious user or source IP address. These variants are called intrusion prevention systems (IPS).

Below are five excellent free IDS technologies to consider for your network.

Snort, available for Windows, Fedora, Centos, and FreeBSD, is an open-source network intrusion detection system (NIDS) that can perform real-time traffic analysis and packet capture on IP networks.

It performs protocol analysis, content search and comparison, and can be used to detect various attacks and probes such as buffer overflows, stealth port scans, CGI attacks, SMB probes, OS fingerprinting attempts, and many more.