It is a data integrity assurance software aimed at detecting and reporting accidental or malicious changes to data.

The following answers are incorrect :

Nessus is incorrect as it is a vulnerability scanner used by hackers in discovering vulnerabilities in a system.

Saint is also incorrect as it is also a network vulnerability scanner likely to be used by hackers.

Nmap is also incorrect as it is a port scanner for network exploration and likely to be used by hackers.

Reference :

Tripwire : http://www.tripwire.com

Nessus : http://www.nessus.org

Saint : http://www.saintcorporation.com/saint

Nmap : http://insecure.org/nmap