Originally posted here by rowdy_yates

hmm. here is one.. gives a kinda explination.

proDETECT "proDETECT is an open source promiscuous mode scanner with a GUI. It uses ARP packet analyzing technique to detect adapters in promiscuous mode. This tool can be used by security administrators to detect sniffers in a LAN. It can be scheduled for regular scanning over periods. It also has some advanced reporting capabilities such as SMTP reporting. Full source code is included." read more...