Hi All,

I remember back some time ago that someone asked the question regarding how to detect someone sniffing your traffic. Well I found a tool that may do this:

proDETECT is an open source promiscious mode scanner with a GUI.It uses ARP packet analyzing technique to detect adapters in promiscious mode.This tool can be used by security administrators to detect sniffers in a LAN.
Here is the link to the source: