Nebula is a data analysis tool that automatically generates intrusion signatures from attack traces. It runs as a daemon that processes data submitted from honeypots. New signatures are published as Snort rules and can be used to defend a network from future intrusion attempts.
You can download it from the following link: https://packetstormsecurity.com/files/download/66835/nebula-0.2.2.tar.gz
Source: https://packetstormsecurity.com/files/66835/nebula-0.2.2.tar.gz.html