NetDiff is a network reporting tool written in perl that runs nmap portscans of a specified network or networks and stores the results to a MySQL database. It can then report the differences between successive scans, giving administrators a snapshot view of recent changes on their network.
This report is very useful for network maintenance and monitoring, it will automatically let you know when:
A new host is added to the network.
A host is shut down or disconnected from the network.
A service has stopped running.
A new service port has been opened.
Additionally, if version and OS scanning is enabled, the report will list those differences as well, telling you if:
A server daemon was upgraded or patched.
The host's operating system was upgraded or changed.