Mac networking: unknown computer in sidebar

[HYHYBT]

In Finder windows, there's a "shared" section of the sidebar that's supposed to show other computers you can connect to. Usually, at home, the only thing there is my old G4 Powermac serving mostly as a DVR. Others sometimes appear when I'm at a public hotspot, but today and yesterday, here at home, there's been one named 'george' that I know nothing about except that it's a PC. It doesn't belong to anyone I know and isn't anywhere that ought to be in range of the wifi network. I changed the network name and password, set it to invisible, and turned the power down to 50% and 'george' was back in seconds. Also, yesterday I did some filekeeping work on my cousin's Macbook. His and mine were connected by target disk mode and have never been on the same network, but today it's showing up in my sidebar as well, despite being an hour away. I can't actually connect, but the fact that it's appeared, and the next day instead of immediately, is a bit worrisome (though not as much as 'george'; at least I know my cousin.) In case it's relevant, the network consists of Apple's Airports.

How worried ought I to be about this, and what, if anything, should I do to stop it?

[EvilEmpryss]

I believe (based on my experience in my own neighborhood with a Mac network), is that you're seeing someone else's comuter on their wifi network, not your own. Yours sounds secure, with the passwords and being set to invisible, but "George" is running his computer as visible, so your computer is just being nice and telling you it's there. When you go to "Join Other Network", do you see any other than your own? I'm betting that you will, and that it's not secure.

As for your cousin's MacBook still showing up, I've never had that happen before. Not to sound silly, but did you properly disconnect the two computers and then restart yours?

[HYHYBT]

"Join Other Network" doesn't show anything but places to type in the name and so forth. The Airport menu isn't showing anything but mine now either. It does sometimes show the networks of two of the neighbors, but not their actual computers.

George disappeared earlier this afternoon, and my cousin's computer vanished just a few minutes ago. I'm not going to worry about it too much.

[EvilEmpryss]

Sorry, I didn't finish the directions. Once you click on "Join Other Networks", click the "Show Networks" button. You should see your network with a black padlock next to it because it's password protected (and please say you didn't use anything resembling "password" as your password... I swear, the number of networks I've been able to access because they didn't have a decent password is sickening). Any other names are other people's networks that are close enough for your computer to pick up. It doesn't mean that your router is picking them up -- it means that their router is strong enough to broadcast their signal all the way to you. Anything without a padlock next to it is an unsecured network. If you're not seeing George right now it may be that they don't have their computer on. As soon as they turn it on you'll probably see it pop up again.

I'm nosey so I like to know what other networks are in my area. I like my neighbors, so when I saw that theirs was wide open, I gave them a heads-up. Someone near my doctor's office, though, has theirs unsecured, which allows me to surf the web while I'm win the waiting room.

[PixelJockey]

I had a similar situation on my home network which I eventually traced to a client I had an Apple Remote Desktop connection to... turns out the phantom pc laptop was logging onto their network and showing up as an option in my network places. This can also happen with any machine which you share a back-to-my-mac connection to (or any machine on the same network as a machine you have a connection to). The fact that it immediately re-established connection after you changed your password suggests to me that it's not someone tapping your network, it's you inadvertently tapping theirs... unless you're using WEP security (which can be hacked using an easily downloadable program in a few seconds) on your Airports.

[HYHYBT]

Right, but george isn't a network. it's a PC. It shows up in Finder windows, not in the Airport menu, and sometimes if I click on it I can see its shared folder. It was on again this afternoon, but only for half an hour or so. The only machine not in my physical possession that I have ever had (or tried to have, at least) a Back-to-my-Mac connection with is Mom's, which is the only computer in her house and is connected by ethernet cable. Though if george disappears exactly when my MobileMe subscription ends (Dec 31st) that would certainly be a clue.

I suppose I could ask, by typing up a letter and leaving it on george... but somehow that doesn't seem like a good idea. And it might well go unfound, unless I also threw in enough other junk to fill its free space.

As for my cousin, if his shows up again I'll just ask him whether the times agree with when he has it on and whether he can see mine.

WPA2 personal, by the way. Because of who else uses the network, I couldn't make the password complex, but it's not anything you're likely to guess and doesn't appear in the dictionary. Besides, we have woods on two sides, and the signal doesn't reach either the street or the property line the other way.

[EvilEmpryss]

I think I may not have been clear: George is showing up in your Finder because your computer is picking up George's network, and George is a computer on his unprotected network. Macs like to be helpful, and because your Mac can see George, it's telling you he's there for you to communicate with by listing him in your Finder. You're obviously picking up his network because if your network is protected than he's not logging into yours. George being around has zero to do with your MobileMe account (though it might explain your cousin's computer showing up; I don't have a MM account, so I don't know for certain).

If you want to verify that George is showing up via *his* network being unprotected, then the next time you see George in your Finder, go to "Join Other Network" and then click on "Show Networks". A network other than your own should show up in the list. It may not be named George, but I guarantee it will not have a little padlock next to it. *That* is how you're seeing George the PC on your Mac's Finder.

Having a PC of my own on my Mac network, I can tell you that unless George regularly checks his shared folder (not likely, since he's not savvy enough to have protected his system), he won't find any letter you write to him. If you want to make sure your computer stops seeing George, there's a few things you can do:

Open System Preferences --> Network Preferences
Click "Ask to join new networks"
Click "Apply" (this will make sure that anytime your regular network is unavailable, it will ask before joining just any old network that's open)
Click "Advanced"

Under the Airport tab, I'll bet you find your home network, your Mom's network, and your cousin's network (the three places you mentioned in your posts). If there are any network names you do NOT recognize, click on them and click the minus sign below to remove them from your list. Anything you keep in this list your Mac will consider a "known" network, meaning you're giving your computer permission to log into it without asking you.

If you want to make sure that you won't pick up George's network again, uncheck the "remember any network this computer has joined" option. It should leave your home network information in place, it just won't save any new network information if you were to, say, go to Panera Bread and log in there.

Click Ok
Click Apply

You can exit System Prefs and go on about you day. You should no longer see George. I hope this helps. The thing I hate most about being able to see other people's stuff is that I have the nagging suspician that they can see mine, too, even though my computer is technically "invisible", and that creeps me out. Get your computer off George's network so his lack of safe computing doesn't wind up infecting your computer. Good Luck!

[HYHYBT]

Nope. george is visible right this moment, and the only network listed is my own. On the occasions when there are others, they have padlocks. Really.

I suspect that if I were to put 106 GB in george's shared folder (the amount of free space the Finder says is available) I'd get some attention, but probably not a good idea even if it were to stay connected long enough to do it.

And while I was typing this, it disappeared again. Good riddance. I give up. Besides, there's nothing in my shared folder and anything else would require a login password... which also isn't "password." And, though I haven't tried lately, I think george's owner would have to go looking for my computer rather than having it just tossed unasked into Explorer windows.

Thanks for the help, though.

[Ironclad Alibi]

Are there any files in george's shared folder that might identify who he is?

An alternative to adding files is to rename or delete (if you're feeling mean) files from george's shared folder.

[EvilEmpryss]

The problem is that a PCs shared folder is separate from the documents folder. The user has to intentionally put folders into the shared folder or there won't be anything there. If George isn't using his PC to transfer files to other computers in his little home network he may not even know the shared folder exists.

And messing with any files already in George's shared folder is just malicious. A file titled GEORGE-READ-ME warning him to secure his network with a password should be all it takes... IF he's paying attention. If you're bored, then drop a copy of the file into his folder every time his computer shows up. But please don't change anything already there.

[Broomjockey]

An alternative to adding files is to rename or delete (if you're feeling mean) files from george's shared folder.

He~ey~ That's computer trespass, and illegal! That's not cool! Be with the cool kids, don't mention doing illegal shit in public! Remember, only YOU can prevent computer trespass. By NOT DOING IT.

[Eric the Grey]

What I want to know is did George have anything cool in his shared folder?

Unfortunately, other than smart-assed comments, I have nothing to offer.


Eric the Grey