I found a new free tool that can help detect network sniffers on your network. The new tool, Promqry 1.0, was developed by Tim Rains at Microsoft. Rains said that many network sniffer detection tools rely on bugs in the operating system and sniffer behavior for their discovery work. Promqry is different in that it can query systems to learn if any have a network interface operating in promiscuous mode, which as you know is a mode commonly use by network sniffing software. A command line version and a version with a GUI are available at Microsoft's Web site.