If you are paranoid about people ARP spoofing or flooding on your network you can use ARPWatch-NG, ARPWatch-NG is a continue of the popular original ARPWatch from ftp://ftp.ee.lbl.gov/.

ARPWatch monitors MAC adresses on your network and writes them into a file, last know timestamp and change notification is included.

It can be used it to monitor for unknown (and as such, likely to be intruder’s) mac adresses or somebody messing around with your ARP/DNS tables.

There have been quite a few fixes lately, so it’s recommended of course to get the latest version!

arpwatch NG 1.5:

try to report error on startup better _ arp.dat _ ethercodes.dat [FIXED]

arpwatch NG 1.4:

try to report _all anomalities via the report function _not syslog [FIXED]

mode 2 _ make action list parseable [FIXED]

further static’fy local functions in arpwatch.c [FIXED]

ethercodes updated from nmap-4.11 and removed old ones [UPDATED]

arpwatch NG 1.2:

on make install also install man-pages [FIXED]

ethercodes updated from nmap-4.00 [UPDATED]

You can download the latest version of ARPWatch here.