Open Source Tripwire

Open Source Tripwire is a free software security and data integrity tool for monitoring and alerting on specific file change(s) on a range of systems originally developed by Eugene H. Spafford and Gene Kim. The project is based on code originally contributed by Tripwire, Inc. in 2000. It is released under the terms of GNU General Public License.

It works by creating a baseline database, and then regularly comparing the state of the file system with the database. If it detects changes (e.g. addition or modification of some files), it includes these changes in its report, so that the security administrators could check these changes.