Is there a good host based software IDS tool? Preferably something centralized and that can be placed on linux or windows boxes?
I have used AIDE before, many moons ago. It worked well. Essentially it creates a hash of all the files you specify checking them periodically for tampering.
AIDE works well for me with an hourly cron job checking the files against the database and emailing me the results (if any)
Go with OSSEC/HIDS, it substitues for using multiple tools like we had to do in the past. Very solid system.
Yea, OSSEC seems to be a very solid system. I would also recommend using this as part of your security solution.