Blocking malicious traffic in PowerDNS using DNS blackhole

Blackholing traffic is a commonly used technique to prevent malicious traffic from reaching its intended destination. This technique involves dropping packets before they reach the targeted server or endpoint. One way to accomplish this is through DNS-based blackholing, which involves redirecting DNS queries for malicious domains to a non-existent IP address. This causes the client to believe that the domain does not exist, effectively blocking traffic to the intended destination.

To implement DNS-based blackholing using PowerDNS, you can configure a zone file with the necessary DNS entries. For example, to block traffic to the domain example.com, you can create a zone file with the following entries:

$ORIGIN example.com.
@ IN SOA ns1.example.com. admin.example.com. (
  2021032401 ; serial number
  3600 ; refresh
  1800 ; retry
  604800 ; expire
  86400 ; minimum TTL
)
@ IN A 127.0.0.1
* IN A 127.0.0.1

In this example, the @ IN A 127.0.0.1 entry maps the root domain to the loopback IP address, effectively blocking traffic to any subdomains or endpoints. The * IN A 127.0.0.1 entry is a wildcard entry that blocks traffic to any subdomains of example.com.

You can customize this configuration to block traffic to specific subdomains or endpoints by creating additional entries in the zone file. For example, to block traffic to the subdomain www.example.com, you can add the following entry:

www IN A 127.0.0.1

DNS-based blackholing is a useful technique for mitigating malicious traffic and protecting your network from attacks. By using PowerDNS to configure zone files, you can easily implement this technique and customize it to suit your specific needs.