How do you implement DNS firewall and response policy zones (RPZ)?

1 What is DNS firewall?

DNS firewall is a feature of BIND that enables you to apply rules to incoming and outgoing DNS queries and responses. These rules can be based on various criteria, such as the source or destination IP address, the query name, the response type, or the DNSSEC status. You can use DNS firewall to block malicious or unwanted traffic, redirect queries to alternative servers, or enforce security policies.

2 What is RPZ?

RPZ stands for response policy zone, which is a special type of DNS zone that contains rules for modifying DNS responses. RPZ works in conjunction with DNS firewall, as it allows you to specify how to change the response data, such as the IP address, the CNAME, or the NXDOMAIN status. You can use RPZ to prevent access to malicious or phishing domains, redirect traffic to safe or informative pages, or implement custom DNS services.

3 How to configure DNS firewall and RPZ?

In order to configure DNS firewall and RPZ, you need to edit the named.conf file of your BIND server and add three sections. The first is a response-policy option which defines the RPZ zones and their order of precedence. These can be local files or remote sources, and you can also set recursion and logging level options. The second section is a view section which defines the scope and access control of your DNS firewall and RPZ rules. Match-clients and match-destinations can be used to specify which clients and servers are affected by the rules, as well as other options such as recursion and forwarding. The third section is a zone section for each RPZ zone which defines the type, file, and master of the zone. Master type can be used for local files or slave type for remote sources, with additional options such as refresh and retry available.

4 How to create RPZ rules?

In order to create RPZ rules, you need to edit the zone file of your RPZ zone and add several records. This includes an SOA record that defines the serial number, refresh interval, and expiry time of the zone, an NS record that defines the authoritative name server of the zone, a TXT record that defines the human-readable description of the zone, and a policy record that defines the action and data for modifying the DNS response. Different types of policy records can be used depending on the desired outcome, such as A, AAAA, CNAME, DNAME, or NODATA. Wildcards and regular expressions can also be used to match multiple query names.

5 How to test DNS firewall and RPZ?

To test DNS firewall and RPZ, you need to use a tool that can send and receive DNS queries and responses, such as dig, nslookup, or drill. You can use different options and parameters to specify the source and destination IP address, the query name, the query type, and the DNSSEC status. You can then compare the results with and without the DNS firewall and RPZ rules, and check if they match your expectations.

6 How to monitor DNS firewall and RPZ?

To monitor DNS firewall and RPZ, you need to use a tool that can collect and analyze the logs and statistics of your BIND server, such as syslog, rndc, or dnstap. You can use different options and commands to specify the level and the format of the logging, the type and the frequency of the statistics, and the destination and the output of the data. You can then use a graphical or textual interface to visualize and interpret the data, and identify any issues or anomalies.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?