Network scans finding matching closed ports on two different networks?

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trixiedeea

Aug 18, 2018
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So let's say I have two ip addresses in two different physical locations - work and home - using two different isp's - Verizon and at&t - and a network scan shows the same three closed ports - 139, 445 and 45514 - on both ip's. Does this mean they are networked together somehow?
 
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NMAP scan the LAN. The only way to scan the wan side is from a server on the internet....now if you have your own server in a hosting center and are running nmap that is another story....i suspect that is not the case though.

Not responding does not mean its open.
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trixiedeea

Aug 18, 2018
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Yes. I agree. My question is WHY would two networks on two different ISP's with two different IP's be reporting THE SAME THREE closed ports? HOW could that happen with such specific ports. If you dont know please dont answer
 
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bill001g

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Aug 9, 2012
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It is highly likely you are not testing correctly. More the question would be why ONLY those three ports closed. The more common result when you scan from the internet is all ports are closed. This is the standard unless you have set your router to allow more ports through.

In most cases any scan from the internet is testing your router not the ISP. To actually test the ISP you would have to setup servers that actually respond on the ports you are testing and then scan.

If you scan a port that no server is using it is considered closed even if the traffic technically makes it all the way in...nothing is there to respond so it will be marked as closed even though network wise it is actually open.

Because I doubt you have a server configured to listen to every port it again makes me think you are not correctly testing.

If you are running some program on your pc to scan this you are scanning the LAN and then it mostly depends on what the router is configured to response and not respond to on its lan port.
 
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BuddhaSkoota

BuddhaSkoota

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Aug 16, 2014
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One can only guess the cause of the problem when you don't provide specific details, like what network scanning application you are using to test ports?

Those 3 ports being closed signifies absolutely nothing except that the software is probably configured to test only those specific ports.
 
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trixiedeea

Aug 18, 2018
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Hi bill001g

Thanks for your detailed response. You are correct it is the routers as previously mentioned it is a WAN scan I'm scanning using nmap set up to scan ALL 65535 ports - BuddhaSkoota- I'm doing the test right. I get no responses from every other port but on BOTH networks the SAME THREE PORTS respond as closed. That is one hell of a coincidence. Especially since none of the three are the common ports like 80 or 443. COULD IT BE THAT A COMPUTER ON EACH IS NETWORKED TOGETHER THUS CREATING THE ACK RESPONSE AND EXPLAIN WHY IT'S THE SAME 3 PORTS ON BOTH NETWORKS? That's all I'm asking. What are the situations in which the same three ports would be responsive on two different networks, assuming obvs that a VPN or skype or xbox live or something is joining them
 
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bill001g

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Aug 9, 2012
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NMAP scan the LAN. The only way to scan the wan side is from a server on the internet....now if you have your own server in a hosting center and are running nmap that is another story....i suspect that is not the case though.

Not responding does not mean its open.
 
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