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Freeware detects insecure wireless networks

Learn how NetStumbler, a free utility, helps network admins determine if a wireless network is insecure or just lacking in signal strength.

Wireless networking has become a convenient way to connect computers without the hassle of running cable between machines. But if it's not properly secured, it can be a loophole through which crackers can hijack free network access.

Network Stumbler, or NetStumbler as it's more commonly called, is a free utility that can help a network administrator determine if one or more wireless networks in the organization is insecure or just lacking in signal strength. It works with 802.11b/a/g networks on Windows and will continue to be upgraded as changes in wireless network protocols and standards evolve.

When you launch the program, the first thing it does is try to disable the Wireless Zero Configuration Service, since the service must be disabled to give the program direct access to the wireless card's configuration. The program then attempts to scan all channels on all available wireless devices and retrieve what networks are available on each.

If you click on the name of a discovered network, the program displays a graph that shows the signal strength of the network in question. The graph, which is updated regularly, shows signal readings as well as noise readings. If a network is weak in a particular area, this feature helps determine if that is because of interference from other radio sources or simply a lack of strength on the part of the transmitter.

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The "Filters" tree in the program's left-hand pane lets you filter the discovered networks by various parameters. For instance, with the "Encryption Off" filter, you see all networks that are not using encryption, which provides a quick way to see if a given network is not secured. Likewise, the "ESS (AP)" filter lets you see all access points with publicly available names – another common security problem, since a network with a publicly broadcast name can be easily infiltrated.

About the author

Serdar Yegulalp is editor of the Windows Power Users Newsletter.

This tip originally appeared on

This was last published in December 2005

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