How to find out if someone is using My Wireless Network

[Kimbo]

I think my neighbors might be using my Wi-Fi. How can I tell?

The easiest way to tell if someone is using your Wi-Fi network is to use a free program like Wireless Network Watcher. This program lists gadgets currently connected to your network, so you can spot anything that looks out of the ordinary. If your suspicions were created because you’ve noticed your network slowing, there may be other things causing it. This could be your router or typical slowing caused by high traffic peak times. Before blaming your neighbor, try these tips for testing your Wi-Fi network.

Here is the free software I use, it's free and so far I had no issues with it!!!

http://www.nirsoft.net/utils/wireless_network_watcher.html