1

other computers of my ISP appears here

viewing the network page

I could see many computers under "Network" section on the left sidebar of Windows Explorer, but I am the only one who uses computer on my home.

So I suppose all those computers are also using the same Internet Service Provider as me, and we're both inside the same "local" network or so.

The network setup on my home is simple, just my computer connected to a Wifi Router, then to a fibre optic router/modem.

I don't know if this is a security issue, but my feeling is that this is not a normal thing to happen.
So, is this a serious issue?

  • Did you tell/ask your ISP about it? This seems like a security issue. – Luc Jun 25 at 7:05
  • I didn't, and also guess it will be pointless, my ISP seems to have a poor tech support. Also unstable connection, frequent downtimes, RTO, etc. – topher Jun 25 at 7:16
  • Seems like you have access to all ISP customers in your area. This is a security issue. – Maurice Jun 25 at 7:21
  • You should definitely let your ISP know about this. Being able to reach into other customer's networks is not okay. If they have a security contact (like security@example.com), that would be the way to go; if not, try to impress upon the support staff that this is a serious security breach and they should connect you to a technical person, or send a technical person a message/ticket. – Luc Jun 25 at 7:24
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One obvious way this could happen is if your WiFi is not very secure, and a lot of neighbors are using it. That's probably not the case - this is a very large list of local devices for that, and people often set a network they don't control as using the "public" firewall profile (it's the default, in fact), which (by default) turns off Windows Networking (SMB) including discovery.

The other way this can happen is if your home is sharing a subnet with a lot of other computers, probably from other nearby homes. This can definitely happen in apartments or condominiums, where there might only be one line into the building and then all the residents are on a subnet behind a router using network address translation (NAT). It could also happen with an ISP putting a lot of customers behind a NAT to avoid needing too many external IP addresses. It's odd that your WiFi router wouldn't create its own subnet that makes it impossible to directly address the other computers, but depending on how it's configured that's certainly possible.


Security-wise, you're probably OK as long as you have a really good password on your machine and don't open your firewall for programs that don't need it (or that have known vulnerabilities). However, it's definitely not ideal. If you're sharing a subnet with computers you don't recognize, they could be doing things like ARP spoofing (which would cause all of your network traffic to travel through their computer, allowing them to read and even tamper with all unsecured traffic) or DNS poisoning (which would cause your computer to think that a domain name maps to a hostile machine). The attacker could also just be doing things like trying to brute-force your password (for Windows networking, remote desktop, SSH if you have it enabled, etc.) even if it's not possible to reach those services from the Internet.

I'd recommend first of all figuring out why those computers are reachable - are the on the same WiFi as you, or on the same subnet anyway, or what - and removing them if possible (set a good WiFi password, etc.). I'd also consider changing the network profile in Windows to "public"; it'll block a bunch of stuff that is considered unsafe to expose to potentially-hostile networks.

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    "> It could also happen with an ISP putting a lot of customers behind a NAT to avoid needing too many external IP addresses" -- I think it's correct, I often get IP-banned on certain sites, even though I haven't opened that site (and even google repeats the "I'm not a robot" test frequently). Also I'm sure that my WiFi network is secure, and it's range only covers half of my house, those computers are probably my neighbors'. – topher Jun 25 at 7:33
  • I agree with topher. My best guess here is that it's a WISP (Wireless ISP) or similar operating utilizing poorly-configured CG-NAT. – AbsoZed Jun 25 at 19:10

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