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Since open ports are a security risk, I would like to know which ports are open to the Internet (outside my network). I wouldn't think of all open ports as security vulnerabilities just the ones exposed to the Internet. Is there a tool to check this?

Vilican
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toddlermenot
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    I think you are looking for [nmap](https://nmap.org/) – BadSkillz Dec 24 '15 at 10:34
  • You should specify within your question on which OS you would like to run such a tool, if you are interested in a software service provider. To avoid useless answer, and to be seen as a new born question, specify what you tested so far. – dan Dec 24 '15 at 11:05
  • @danielAzuelos It is right there on the title ("Windows"). It is also there on the tags. – toddlermenot Dec 24 '15 at 11:10
  • @BadSkillz nope. Nmap doesn't give an outside view of my network. – toddlermenot Dec 24 '15 at 11:10
  • Do you mean "from Windows"? If yes, fix your title please. – dan Dec 24 '15 at 11:12
  • Downvoters, My first question in this site. Please comment your reason, so that I can get it corrected. – toddlermenot Dec 24 '15 at 11:12
  • @danielAzuelos: No, I meant "in windows". I have rearranged the prepositions in the title so that it is more clear now. – toddlermenot Dec 24 '15 at 11:16
  • Pointing nmap to your external ip will scan it as if it was from an outside source. Else take a laptop and scan it from another location. – BadSkillz Dec 24 '15 at 12:00
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    The "in Windows" isn't clear. When you perform a port scan you do it "from" a source (running a given OS appropriate to test vulnerabilities) "toward" a target (running a given other OS appropriate to have vulnerabilities). Within this context, `nmap` is far from a stupid answer. – dan Dec 24 '15 at 12:24
  • @BadSkillz, that only works if you've got a NAT router, that router supports loopback routing, and it performs the loopback "outside" both NAT and firewall. I've found very few devices that will do it. – Mark Dec 24 '15 at 19:43
  • Toddler, questions asking for tool recommendations are off topic for this site. See the help section for more information. – Neil Smithline Dec 25 '15 at 05:34
  • @NeilSmithline, this isn't a tool recommendation question, this is a "what sort of tool do I use to solve this problem" question. – Mark Dec 26 '15 at 00:47

2 Answers2

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What you're looking for is a port scanner. Specifically, you're looking for one hosted on a server somewhere to give you an outside look at your network. There are a great many of them out there, of varying features and usefulness.

Mark
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  • Thanks, care to name a few popular ones? My googlefu is failing as all I am getting is "nmap" which does not represent the outside look of my network. – toddlermenot Dec 24 '15 at 11:09
  • I can't recommend any particular one, since I haven't used them in years. I've got root-level access to computers on two different networks, so I can just use `nmap` from one to scan the other. – Mark Dec 24 '15 at 11:20
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You can check server's open ports with nmap command like this: sudo nmap -O remote_host

For example running this for example.com domain:

sudo nmap -O example.com

Starting Nmap 7.60 ( https://nmap.org ) at 2019-04-10 14:39 EEST
Nmap scan report for example.com (93.184.216.34)
Host is up (0.068s latency).
Not shown: 997 filtered ports
PORT     STATE  SERVICE
80/tcp   open   http
443/tcp  open   https
1935/tcp closed rtmp
OS fingerprint not ideal because: Didn't receive UDP response. Please try again with -sSU
No OS matches for host

OS detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 13.24 seconds

More examples with nmap: https://www.digitalocean.com/community/tutorials/how-to-use-nmap-to-scan-for-open-ports-on-your-vps

Maksim Luzik
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