Hi,

I have mac filtering setup on mine and if someone tries to access the network then a warning flashes on the AP and I get a pop up if I visit the setup page. This tells me what the MAC address the would be network user is. I think there's a record made in the log but I'm not sure how long the log is kept for.

If your worried you can

dissable the SSID broadcast then no one will find you when they search for networks
enable MAC filtering then only PC's on your list are allowed in
enable WEP encryption. Then your data is unreadable unless they have a key supplied by you. The open type is best and not the shared key.