Wireless Network Watcher
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Full user review
"Does what it says it does."
Super simple to use. The layout is also simply put together and simple to understand. You can make an HTML report on any IP address it detects. It beeps when someone else uses your wireless. Good software if privacy and wireless hijacking is a factor. It's a small utility and best of all it's free.
The avatar and layout could use a little modernization as it looks like something Windows XP left behind.
All in all this software does not stop anyone from jumping into your WI-FI. It simply let's you see who's getting a free ride on your WI-FI. Nevertheless it is useful if Privacy and Hijacking is a concern.