How can you tell if somebody is connected to my wireless router

[spec74]

My router seems to be active all the time even though i'm not doing anything online. Is there a way to find out if somebody is connected to my router or not? Also how do you keep somebody from connecting to my router?

 

[T3C]

What kind of router?
Just log into it and look at the wireless client mac table. Deny all but your own mac's, put in a WEP key.

 

[spec74]

I have linksys wrt54g V4

 

[RebateMonger]

Remember too, that even if nobody is CONNECTED to your router, if you aren't using WiFi encryption, anybody nearby can record all your traffic to/from your WiFi router. Use encryption. Hopefully WPA or WPA2, since WEP isn't hard to crack.

MAC address restrictions don't help against anybody who's determined, since it's easy to determine the exisiting MAC addresses and impersonate them when those PCs are turned off.

 

[JackMDS]

Almost all Wirelee Router has few LEDs.

The Wireless LED indicate Wireless traffic.

Tthe WAN or Internet LED indicate something happens at the Internet port.

Most Cable Internet?s WAN ports of the Routers flicker all the time even if No one is using the Internet from inside the LAN.