Jump to content
blacter

Strangers showing up on my Shared computers list

Recommended Posts

One of Leopard's cool features is how the sidebar neatly lists shared computers. We'll I looked at that neat list the other night and saw a couple of shared computers that weren't part of our home network.

 

Very puzzling, I thought, especially since we're behind a router. So I did a search and came across this thread on the Apple Discussion Forums.

 

Others were seeing the same thing and someone who seemed to know what he was talking about said that this phenomenon is to be expected if your ISP is a cable company since all the subscribers are essentially part of a common Wide Area Network.

 

Could that be true? If so, why don't I see hundreds of computers instead of just two or three. Any, most to the point, should I be concerned that those cable neighbors can mess with my stuff?

 

Thanks, guys.

 

...Barry

Edited by blacter

Share this post


Link to post
Share on other sites
One of Leopard's cool features is how the sidebar neatly lists shared computers. We'll I looked at that neat list the other night and saw a couple of shared computers that weren't part of our home network.

 

Very puzzling, I thought, especially since we're behind a router. So I did a search and came across this thread on the Apple Discussion Forums.

 

Others were seeing the same thing and someone who seemed to know what he was talking about said that this phenomenon is to be expected if your ISP is a cable company since all the subscribers are essentially part of a common Wide Area Network.

 

Could that be true? If so, why don't I see hundreds of computers instead of just two or three. Any, most to the point, should I be concerned that those cable neighbors can mess with my stuff?

 

Thanks, guys.

 

...Barry

 

I'm not familiar with the specifics, but I would suspect that you are seeing those machines on the same "subnet" as your computer. Features like this tend to rely on broadcasting of UDP packets to see what's out there listening. Depending on how your cable company allocates individual homes to subnets and how many of those homes have a computer running at any particular time, that could result in a relatively small number of computers showing up at any time.

 

Without being sure of what's going on, it does seem possible that outsiders could get into your system using UDP-based protocols. It's unlikely that they'd be able to see files, but I'm not familiar enough with the different protocols to be sure.

 

I've never noticed this problem in my neighborhood, and I know that lots of us have comcast cable. I'm curious about why it would happen for you and not for me.

 

What kind of router are using? I wonder if there are certain router settings that make a difference.

 

- Tim

Share this post


Link to post
Share on other sites
I'm not familiar with the specifics, but I would suspect that you are seeing those machines on the same "subnet" as your computer. Features like this tend to rely on broadcasting of UDP packets to see what's out there listening. Depending on how your cable company allocates individual homes to subnets and how many of those homes have a computer running at any particular time, that could result in a relatively small number of computers showing up at any time.

 

Without being sure of what's going on, it does seem possible that outsiders could get into your system using UDP-based protocols. It's unlikely that they'd be able to see files, but I'm not familiar enough with the different protocols to be sure.

 

I've never noticed this problem in my neighborhood, and I know that lots of us have comcast cable. I'm curious about why it would happen for you and not for me.

 

What kind of router are using? I wonder if there are certain router settings that make a difference.

 

- Tim

 

Thanks, Tim. Very interesting. Our cable provider is a small local outfit in Bend, Oregon. Given how much trouble they had installing a cable card in my Tivo, I wouldn't be surprised if they didn't have all the settings quite right in their system. I actually replaced an old Linksys router in an attempt to fix this problem. The new one is a fancy D-Link DGL-4100. It didn't fix the problem (but made my web browsing noticeably snappier).

 

...Barry

Share this post


Link to post
Share on other sites

Not having Leopard, I don't even know if this is what is supposed to happen, but can you click on their computers and 'look' at them?

Share this post


Link to post
Share on other sites
Thanks, Tim. Very interesting. Our cable provider is a small local outfit in Bend, Oregon. Given how much trouble they had installing a cable card in my Tivo, I wouldn't be surprised if they didn't have all the settings quite right in their system. I actually replaced an old Linksys router in an attempt to fix this problem. The new one is a fancy D-Link DGL-4100. It didn't fix the problem (but made my web browsing noticeably snappier).

 

A simpler explanation just occurred to me that you might want to check first: Are you using a wireless network without security enabled? If so, it is possible that other machines in your vicinity are sharing your network. That would definitely make them visible on the sharing list.

 

Assuming that is not the answer, you should next look at your router's DHCP and/or NAT settings and let us know how they are set up. In my case, my router is set up to distribute IP addresses to my network (and only my network) via DHCP. In simplest terms, it means that a virtual subnet is set up just for those machines connected through my router. UDP packets won't typically pass between my network and the outside world. If, on the other hand, you are set up so that your ISP provides IP addresses to you, you could be ending up on their subnet. Switching your router should prevent this problem, and will be more secure as well.

 

- Tim

Share this post


Link to post
Share on other sites

Well, without making any changes to my system, the "shared strangers" disappeared. Makes me think that my cable company ISP was responsible and fixed the problem. To answer the earlier questions, my router is set up to supply addresses on the local network through DHCP. And my wireless network has password protection.

 

Thanks to all,

 

...Barry

Share this post


Link to post
Share on other sites

I noticed the same thing recently. Two different PC servers appeared on my shared network. I am using wireless but it doesn't even broadcast that its there and has as much security as i could have on it. I'm wondering if it's something with my dsl provider.... my computer shouldn't even show up to them....

Share this post


Link to post
Share on other sites

Older cable systems essentially share the local cable run among the neighbors as a single LAN. Thus, your neighbors' usage impacts your available speed. And, by the way, you can view your neighbors' internet traffic - and they can view yours. (Checking out what the neighbors are up to, and what malware they are spreading, is one of my hobbies. ;)

 

Usually a router's NAT function blocks all that foreign stuff from reaching your Mac (or PC.)

 

I wonder if Leopard's new UPnP (Universal Play-and-Play) support breaks through the router's NAT and allows incoming service announcements? UPnP allows NAT traversal. (I.e., a Mac on your LAN could instruct a UPnP-enabled Router to open selected ports to receive external communications. Back-to-my-Mac is supposed to use this, for example, so you don't have to manually configure port forwarding.)

 

I turned UPnP OFF on my NetGear when I installed it (my really old Linksys BEFW11S4 is pre-UPnP.) As an experiment, I just turned it on now, and I see it's magically opened UDP port 4500 (IPsec) already. (This Leopard-running iMac is the only computer turned on here right now.)

 

If your router has UPnP, next time the strangers appear, turn it off and see if they disappear (after their timeout expires.)

Edited by car1son

Share this post


Link to post
Share on other sites

Wow this is very interesting, mskes me not want to upgrade to 10.5. I like to have my network slammed with security as my server is constantly being probed by russian and chinese ip addresses. I would hate for Leopard to open up ports on me with out my consent.

Share this post


Link to post
Share on other sites

But it's nothing to do with Leopard. It's at the router level. If you have your router set up correctly, you should be relatively safe even when you're using *gasp!* windows.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing

    No registered users viewing this page.

  • Who's Online (See full list)

    There are no registered users currently online

×