I have a home network set up, complete with a relatively good password. I'm in Mac OS X 10.6 (Snow Leopard) and have been noticing, on occasion, a computer showing up in my Finder's Shared section, that is not one of my own (the "pe-xpjalle" box pictured below). He has a tendency to come and go.
How can I figure out his MAC address or something, so I can block him? I checked my "Logs and Statistics" in the Airport Utility, and didn't see that computer under DHCP clients. I'd rather not change my password, since I have quite a few devices I'd have to update. Is there any other reason he's show up on my network besides having guessed my password?
Update: I fixed the Dropbox URL above (how embarrassing, I'm new to Dropbox. Thanks for the heads up, Doug.)
Update 2: I tried clicking on "Connect as…" just for the hell of it, and got the dialog below. Now I have even less an idea what's going on than before. I don't have Parallels of VMware running, just the following: Transmission, NetNewsWire, Mail, Things, Safari, iTunes, Photoshop, Pages, Yojimbo, Preferences, AppleScript Editor, Software Update, Airport Utility, and Terminal. I don't think any of those create a virtual network machine, right? And no VMware machine of mine has ever had a name resembling "pe-xpjalle".
Update 3: I just changed my passwords on both my N- and G-only networks, and I'm still seeing this, so I highly doubt that it's someone who's figured out my password (twice now). I'm really stumped.
Best Answer
If he's already broken your encryption, MAC address filtering won't get you anywhere. The easiest and safest way to harden your network is to change the password to your network and enable WPA2 encryption.