An advanced passive OS/network fingerprinting utility for use in IDS environments, honeypots environments, firewalls and servers.

Network-IDS that detects and stops DoS/DDoS attacks by using real-time Cisco NetFlow data.

LIDS is an enhancement for the Linux kernel written by Xie Huagang and Philippe Biondi. It implements several security features that are not in the Linux kernel natively. Some of these include: mandatory access controls (MAC), a port scan detector, fi...

A single compilation of source, binaries, scripts and whitepapers on intrusion prevention systems. The aim is to quickly establish a working IPS within minutes.

A free lightweight network intrusion detection system for UNIX and Windows.

Small daemon that creates virtual hosts on a network (honeypot). Can be used as a virtual honeynet or for network monitoring. For *BSD, GNU/Linux, and Solaris.

Firestorm is a high-performance GPL-licensed network intrusion detection system (NIDS). Features include being fully pluggable, easily configurable, and an extremely scalable signature engine.

fail2ban is a POSIX/Linux tool used to ban IP addresses that generate too many password failures. ssh, iptables, ipfwadm and ipfw are currently supported.

Provides open source application to check for presence of rootkits installed on Linux/Unix machines. Links to security related sites.

AIDE is a file integrity checker that supports regular expressions. Licensed with GPL.