Bind

Hide version
Version might be useful to an attacker that is searching known vulnerabilities on your server. Let’s make its life more difficult by hiding it.

Note that it is not an excuse to run old vulnerable software. The goal is just to slow down attacker in case of newly published security exploit, so you have enough time to update before getting pwned.

To prevent the version being returned edit the file  and add the version line

Response Rate Limiting (RRL)
DNS servers can be abused to perform DoS attacks on other innocent victims. This are several issues for that For more details, read the quick introduction to response rate limiting from ISC (Bind author).
 * attacker will waste your bandwidth while attacking other servers
 * you are seen by the victim as the source of the attack. You can then appear in blacklists which will be an issue for you
 * you are making DoS attacks easier for the attackers and contribute to the problem

Rate limiting allows to render such attacks ineffective while still answering legitimate responses. To enable this, add the block  in file

Listen on public IP
By default, Bind will only reply to queries from localhost. To use it as an authoritative server, you must make it listen on a public IP. Once again the file to modify is  The 3 options to modify are (these should already be there in the file):
 * : List of IPv4 addresses to listen on.  means all. Otherwise you can list IPs:
 * : Same as above for IPv6 addresses
 * : IPs to witch the server will reply to recursive queries (when it need to contact other severs to get the response). This must never contain any public IP.

Firewall
Bind will listen on port 53, on both TCP and UDP.

Reload Configuration
Bind9 can be told to reload its configuration using Warning: This command is working asynchronously. It is recommended to verify that everything was fine using This will show you the last lines of the log. If anything went wrong, it should appear in red.

Test for open recursion
Open recursive DNS servers are really BAD. You can test your server at http://openresolver.com.