Libnids is a library that provides a functionality of one of NIDS (Network Intrusion Detection System) components, namely E-component. It means that libnids code watches all local network traffic, cooks received datagrams a bit (quite a bit ;)), and provides convinient information on them to analyzing modules of NIDS. So, if you intend to develop a custom NIDS, you don’t have to build low-level network code. If you decide to use libnids, you have got E-component ready – you can focus on implementing other parts of NIDS.
You can download it from the following link: https://packetstormsecurity.com/files/download/11642/libnids-1.12.tar.gz
Source: https://packetstormsecurity.com/files/11642/libnids-1.12.tar.gz.html