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Hide or determine BIND version number

Published: 08-05-2013 | Author: Remy van Elst | Text only version of this article

❗ This post is over ten years old. It may no longer be up to date. Opinions may have changed.

The BIND nameserver (and many others) return their version number when queried a special DNS query. This gives exposure and that is most of the time a bad thing. This tutorial shows you how to query DNS servers for their version and how to stop/change your own BIND server version exposure.

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Chaos Query

The following DIG and NSLOOKUP queries will show the version of BIND:

A home router queried with DIG:

dig @ version.bind txt chaos
version.bind.       0   CH  TXT "dnsmasq-2.47"

A Microsoft DNS server queried with nslookup:

nslookup -type=txt -class=chaos version.bind

version.bind    text = "Served by PowerDNS -"

What is chaos or CH class you ask? It is/was a network technology, see the wikipedia page for more info.. There is also the HS class, that stands for Hesiod.

Hide it in BIND

When running a BIND nameserver, edit your /etc/bind/named.conf.options file (or the config file where you have your options) and add the following option:

options {
    version "Not supported";

You can of course put whatever you like in there, for example you can spoof a Microsoft DNS server:

version "Microsoft DNS 6.0.6100 (2AEF76E)";

Or like TransIP does, make it look like your own DNS software:

dig version.bind txt chaos

version.bind.       86400   CH  TXT "TransDNS 2.1.1"

Make sure to reload/restart your BIND servers after the change. Do note that you need BIND 8.2 or later for this option to work.

db.bind zone

You can also add a .bind zone, this way your queries will also be logged and you can block possible attempts.


view "chaos" CH {
  match-clients { any; };
  zone "bind" CH {
      type master;
      file "db.bind";
      allow-update { none; };


$TTL    3600
@       86400       CH   SOA     localhost. root.localhost. ( 
                    2013050801      ; serial 
                    3600            ; refresh 
                    3600            ; retry 
                    604800          ; expiry 
                    86400 )         ; minimum 
@                   CH  NS  localhost.

version             CH  TXT "Microsoft DNS 6.0.6100 (2AEF76E)" 
authors             CH  TXT "" 

However this gets complicated very fast, you need to wrap all your other zones in views as well:

view "default" IN {
  match-clients { any; };

So it's better to use the above options file.

Tags: bind , dns , dnsmasq , exposure , named , tutorials , version