NetStumbler

NetStumbler is a utility that works under Windows and is meant specifically
for 802.11b wireless networks. Under the 802.11 standard, most
wireless hardware vendors are compatible. However, security is the
most commonly overlooked element. NetStumbler has released its software
in an effort to increase awareness of the inherent problems with
wireless communication security, or lack thereof. The objective is to see
that vendors concentrate on security while maintaining the functionality
necessary in wireless products.