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We are having an internal discussion about system naming conventions and there is a disagreement about including the type of OS a system is running in the DNS host record. One suggestion was to include 'win', 'mac', or 'lin' in the A record field for easy identification. Since this gives would-be hackers easy information about a system that they would otherwise have to work for, some people are uncomfortable with this.

Is there any general consensus on this issue? Has NIST (or any other authority) weighed in with an answer? Thanks in advance.

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    What is the motivation to include OS in the A record? What practical use will it have? – Peter Jan 24 '18 at 15:15
  • @Peter One use would be for NAC to have immediate access to OS information so that it knows what agents to scan for before allowing network access. – doneal24 Jan 24 '18 at 15:17
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    @DougO'Neal That's a job better suited to some sort of IPAM solution, not embedding such metadata in the hostname. My organization does the OS-in-hostname thing and I wish they didn't-- hardware and software changes often before DNS gets updated, so it's constantly inaccurate. – Ivan Jan 24 '18 at 18:27
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    I also see no point in creating just another dependency in what are otherwise completely unrelated bits of information. It adds extra work, it will eventually be inaccurate. It won't be long before words like, "The DNS entry says it's Linux - better check if that's true." are heard. – Andrew Henle Jan 25 '18 at 0:18
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    There's actually a specific RR type for this: HINFO. – user54862 Jan 25 '18 at 3:05
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The naming conventions of computers has long been a divisive topic and often the security of a network needs to be put up against the manageability of an environment. I have worked in environments where the server names dictated exactly what that server did, and I've worked in networks with weird naming conventions that did nothing else than tickle the SysAdmin's fancy.

As a Penetration Tester I will tell you that there are a number of trivial ways for me to glean what Operating System a computer is.

  • Nmap does a very effective job of "guessing" what OS a computer is. Try for yourself nmap -A <IP ADDRESS>
  • The MAC address of a computer can be a giveaway in the example of Mac's
  • The services running on a machine can provide you with a good clue as to what OS the system is running (Banner grabbing)
  • If you can get a user on that system to navigate to a website with a BeEF hook embedded or other mechanism to enumerate the machine then you'll easily identify the OS running.

Typically speaking, the Operating System itself isn't of too much interest to me. I'm more concerned as to what the patch level is like of a specific machine, what services are running on it that might be vulnerable, etc. I personally don't think that putting the operating system in an A name is a security risk in and of itself and I know plenty of organizations that utilize a similar naming convention.

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