15. Arpwatch – Ethernet Activity Monitor

Arpwatch is a kind of program that is designed to monitor Address Resolution (MAC and IPaddress changes) of Ethernet network traffic on a Linux network. It continuously keeps watch on Ethernet traffic and produces a log of IP and MAC address pair changes along with a timestamps on a network. It also has a feature to send an email alerts to administrator, when a pairing added or changes. It is very useful in detecting ARP spoofing on a network.