These are a couple of screen shots I took while trying out Netstumbler
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During A short 10 minute ride through a neighborhood, my laptop and Netstumbler discovered 11 wireless networks. Notice in the last column how many of these networks used no encryption. Any wireless notebook within range of these unprotected access points will be able to immediately connect through the access point.
NetStumbler includes a real-time graph of the signal strength. This make it rather easy for someone to determine which specific house they would be connecting to.
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