Automatically Detect File Changes on Your Server
From bashshell.net
AIDE (Advanced Intrusion Detection Environment) is the Open Source version of Tripwire. AIDE takes a snapshot of every file on your server, records it and then will notify you of any changes. This tutorial will show you how to create a script that will automate this process and send you an email of the outcome.
Step #1: Install and Configure AIDE
If you need more information on installation and configuring AIDE.