This is a text-only version of the following page on https://raymii.org:
---
Title       : 	Hide or determine BIND version number
Author      : 	Remy van Elst
Date        : 	08-05-2013
URL         : 	https://raymii.org/s/tutorials/Get_DNS_server_version_and_hide_it_in_BIND.html
Format      : 	Markdown/HTML
---



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 @192.168.1.1 version.bind txt chaos
    ;; ANSWER SECTION:
    version.bind.       0   CH  TXT "dnsmasq-2.47"
    

A Microsoft DNS server queried with `nslookup`:

    
    
    nslookup -type=txt -class=chaos version.bind ns1.metaregistrar.nl
    Server:         ns1.metaregistrar.nl
    Address:        81.4.97.217#53
    
    version.bind    text = "Served by PowerDNS - http://www.powerdns.com"
    

What is `chaos` or CH class you ask? [It is/was a network technology, see the
wikipedia page for more info.][2]. There is also the [HS class, that stands for
Hesiod.][3]

### 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 @ns1.transip.nl version.bind txt chaos
    
    ;; ANSWER SECTION:
    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.

`/etc/bind/named.conf.local`:

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

`/etc/bind/db.bind`:

    
    
    $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 "Raymii.org" 
    

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.

   [1]: https://www.digitalocean.com/?refcode=7435ae6b8212
   [2]: https://en.wikipedia.org/wiki/Chaosnet
   [3]: https://en.wikipedia.org/wiki/Hesiod_(name_service)

---

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