Skip to main content

BIND 9

This guide will provide you with important steps on how to harden your BIND 9 server. BIND (Berkeley Internet Name Domain) is an open source software that implements the Domain Name System (DNS) protocols for the Internet.

It is highly recommended to follow these security principles because the domain name system's service is a crucial part of any network, thus it's necessary to ensure its resilience against attacks.

1. Update Your Systems​

The systems that run BIND 9 should always be up-to-date. This includes the operating system, BIND 9 software, and all the other software running on your system. Updates often include important security patches.

For Ubuntu or Debian-based systems, you can accomplish this with the following command:

sudo apt update && sudo apt upgrade -y

For CentOs or RHEL systems, you can use:

sudo yum update -y

2. Restrict Zone Transfers​

Zone transfers should be restricted to only those IP addresses that need the information. This reduces the risk of DNS cache poisoning and other DNS related attacks.

Edit the BIND configuration file (usually located at /etc/named.conf or /etc/bind/named.conf) and add the following:

options{
    allow-transfer { list of IPs; };
};

Replace 'list of IPs' with the IP addresses that are allowed to receive zone transfers.

3. Enable DNSSEC​

DNSSEC (DNS Security Extensions) is a set of security extensions for the DNS protocol that provides authentication and integrity to the DNS system.

Enable DNSSEC by adding the following to your BIND configuration file:

options{
    dnssec-enable yes;
    dnssec-validation yes;
};

4. Disable Recursive Queries​

Disabling recursive queries will help prevent DNS amplification attacks, where a small query can be turned into a much larger response.

Add the following to the BIND configuration:

options {
    recursion no;
};

5. Rate Limiting​

BIND 9 server can be configured to limit the rate of queries from a client IP address.

Edit the BIND configuration file and add:

options {
  rate-limit {
    responses-per-second 5;
  };
};

This will limit the responses to a client IP address to 5 per second.

6. Use the Latest BIND Version​

Always ensure that you are running the latest and patched version of BIND. Latest versions come with improved security features and bug fixes. Use the following command to check the version:

named -v

7. Run BIND in Chroot Environment​

Running BIND in a chroot environment can limit the damage in case of a compromise as this approach effectively isolates the BIND process.

Consult the documentation of your operating system on how to configure BIND to run in a chroot environment.

Remember, every security improvement you choose contributes to the overall safety of your system and network.

8. Logging​

Implement BIND Logging for troubleshooting and to identify unusual or suspicious activity. This can be implemented by adding the following configuration:

logging {
        channel default_debug {
                file "data/named.run";
                severity dynamic;
        };
};

9. Restricting BIND Process Resources​

The Linux system allows restricting resources available to a service. Here's an example of how you can restrict BIND process:

options {
    max-cache-size 100M;
    max-cache-ttl 3600;
    max-ncache-ttl 3600;
};