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On many technical forums, in order to help solving or analyzing problems with the networks connection, I am asked to run command ipconfig/ifconfig, and show the results in public.

Is this safe?

Do some of the details shown in the results help someone who wants to hack my computer?

Do I have to hide some of the lines shown in the results?

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  • Maybe it could be moved to security.se . . . It was surprisingly difficult to find a list of private addresses on StackExchange that I could link to.
    – Law29
    Apr 30 '16 at 12:55
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You config may include public, private, or otherwise non-public addresses. If there are public addresses or names that resolve to your public addresses, you may wish not to publish them or to mask them, especially if you are posting about configuration problems that could be abused. However, that can also hinder people from helping you, of course.

Usually a computer in a home behind a box will be NATed, and thus only have private IPs, but you might have a hosted server with a public IP.

The following are common addresses that everyone and anyone can have in their configurations, they are safe to publish:

  • 10.0.0.0/8 (10.0.0.0 - 10.255.255.255): RFC1918 "A" private
  • 127.0.0.0/8 (127.0.0.0 - 127.255.255.255): localhost
  • 172.16.0.0/12 (172.16.0.0 - 172.31.255.255): RFC1918 "B" private
  • 169.254.0.0/16 (169.254.0.0/16 - 169.254.255.255): link local
  • 192.168.0.0/16 (192.168.0.0 - 192.168.255.255): RFC1918 "C" private
  • ::1/128 inet6 localhost
  • inet6 link-scope addresses

There are other special addresses, but most people will not have them in their configurations without knowing very well what they are. All special addresses are listed in RFC6890.

For any address, you can consult the IANA list which will give you the Regional Internet Registry if applicable, and the whois server which will give you more information on the range in question. For a public IP address you will certainly be able to drill down to your ISP.

To know your public IP address, search google for "what is my IP address".

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  • thank you and how does a public address look like?
    – tal
    Apr 30 '16 at 5:11
  • Public addresses are most of the rest... I didn't mention addresses starting with 0 or 224-255, you certainly shouldn't have those, but most everything else is public. I'll make an edit with more info.
    – Law29
    Apr 30 '16 at 7:57
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Your IP config will only show private addresses and mac address, your attacker would need to know your public address to gain access to your services.

So no, there isn't harm in posting these results.

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  • my personal computer has private adress only?
    – tal
    Apr 29 '16 at 16:20
  • Well, if you're behind any kind of firewall or router then yes, ipconfig will only contain private addressing info. If you have configured your personal computer to have a public IP address and you're not sitting behind a firewall then I wouldn't recommend posting this info, but that would be an unusual configuration for any machine, especially in a business environment. Post your ipconfig here and we'll tell you whether you've just leaked your public address or not...just kidding :)
    – Ted Quanstrom
    Apr 29 '16 at 17:58
  • Your computer should only have a private address, your ISPs router equipment should NAT your address to a public address, The NAT'd public address will not show up in an IPconfig run from your machine.
    – HAL
    Apr 29 '16 at 18:42
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    It's incorrect to say that ipconfig will never contain public addressing info. Certainly I agree that in 99.9% of configurations it will not, but one can have a host on a public address without a firewall performing NAT upstream of it.
    – Ted Quanstrom
    Apr 29 '16 at 22:56
  • Tedwin, this is about home networking and I answered as such.
    – HAL
    May 2 '16 at 13:11

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