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Let's suppose that I have a router and three computers connected to Internet through that router. When I tried to get the external IP address for each computer, I got the same address. I think this is due to NAT translation. I want to know how a hacker can scan a specific computer of the three computers using nmap and get all information about that specific one.

Mark
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computerSPro
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For the most part, you can't. NAT acts somewhat like a firewall with a "default deny" rule. Unless you set up a DMZ or port forwarding, a computer on the "internet" side of the router cannot make unsolicited contact with the computers on the "private" side.

Mark
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  • Yeah, i mean if behind a router there is a host based on windows 7 and other host based on windows 8. How can i scan only the host based on windows 7 ? – computerSPro Aug 15 '14 at 09:04
  • As I said in my answer, you can't. The router prevents it. – Mark Aug 15 '14 at 09:06
  • Okay, but i wanna know how people can compromise a system if they can't scan it ? – computerSPro Aug 15 '14 at 09:07
  • To greatly oversimplify, by making guesses about the nature of the system. – Mark Aug 15 '14 at 09:09
  • To be a bit of a pedant, NAT doesn't provide any security by itself and could leak internal addresses. See David's excellent answer to a similar question here: http://security.stackexchange.com/a/8773/47496 – Chris Murray Aug 15 '14 at 10:07
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I'm a noob at infosec but can't you do:

nmap 192.168.1.0/24

This assumes you are behind the router

secnub
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  • No, because to do that, you would have to be on that network. The question (which may not be entirely clear) is asking how an external attacker who *isn't* on that network would target a specific computer. – Xander Aug 15 '14 at 21:18