Snort_inline is a project to make the popular IDS product Snort (http://www.snort.org) interface with a firewall. Instead of sniffing packets using the Berkeley packet filter (bpf), snort_inline reads packets from the firewall. The first creation of snort
SnortSam is a plugin for Snort, an open-source light-weight Intrusion Detection System (IDS). The plugin allows for automated blocking of IP addresses on following firewalls:
OSSEC is an Open Source Host-based Intrusion Detection System. It performs log analysis, integrity checking, rootkit detection, time-based alerting and active response.