AIDE (Advanced Intrusion Detection Environment) is a free replacement for Tripwire(tm). It generates a database that can be used to check the integrity of files on server. It uses regular expressions for determening which files get added to the database. You can use several message digest algorithms to ensure that the files have not been tampered with.
You can download it from the following link: https://packetstormsecurity.com/files/download/17835/aide-0.7.tar.gz
Source: https://packetstormsecurity.com/files/17835/aide-0.7.tar.gz.html