Filtering traffic by DNS name and IP address
Out with the Bad

Kurt describes how to keep bad guys out of your network using a targeted filtering approach.
If you're reading this article (and indeed this magazine), you're probably not a huge fan of spam/malware/crapware/spyware, and so on. However, because you're also probably running Linux, you can avoid most of that, right? Just keep the system up to date, install AdBlock, apply SpamAssassin to your email, and so on – easy peasy lemon squeezy.
But, what happens if you have a device that doesn't support AdBlock or antivirus software (e.g., some of the more locked down Android devices)? Or, if you want to block certain domains or networks completely? Firewalling based on IP addresses is great, and you can even find country lists; however, that won't help you block attackers that quickly bounce their domain around multiple providers. If only there were a way to firewall stuff easily at the DNS level.
Response Policy Zones
Back in 2011, ISC, the company that produces BIND and DHCPD, decided this was a problem they wanted to address, so they rather cleverly added RPZ (Response Policy Zone) [1] support in a way that requires no changes to existing DNS client software or to other servers making use of the RPZ server. Basically, RPZ lets you define records to which that the response policy will be applied. These records can be the domain name being queried (QNAME), the IP address being returned in response to the query (IP), the name or domain of any DNS server used to fulfill a query (NSDNAME), and the IP address of any DNS server used to fulfill a query (NSIP).
[...]
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.

News
-
System76 Releases COSMIC Alpha 7
With scores of bug fixes and a really cool workspaces feature, COSMIC is looking to soon migrate from alpha to beta.
-
OpenMandriva Lx 6.0 Available for Installation
The latest release of OpenMandriva has arrived with a new kernel, an updated Plasma desktop, and a server edition.
-
TrueNAS 25.04 Arrives with Thousands of Changes
One of the most popular Linux-based NAS solutions has rolled out the latest edition, based on Ubuntu 25.04.
-
Fedora 42 Available with Two New Spins
The latest release from the Fedora Project includes the usual updates, a new kernel, an official KDE Plasma spin, and a new System76 spin.
-
So Long, ArcoLinux
The ArcoLinux distribution is the latest Linux distribution to shut down.
-
What Open Source Pros Look for in a Job Role
Learn what professionals in technical and non-technical roles say is most important when seeking a new position.
-
Asahi Linux Runs into Issues with M4 Support
Due to Apple Silicon changes, the Asahi Linux project is at odds with adding support for the M4 chips.
-
Plasma 6.3.4 Now Available
Although not a major release, Plasma 6.3.4 does fix some bugs and offer a subtle change for the Plasma sidebar.
-
Linux Kernel 6.15 First Release Candidate Now Available
Linux Torvalds has announced that the release candidate for the final release of the Linux 6.15 series is now available.
-
Akamai Will Host kernel.org
The organization dedicated to cloud-based solutions has agreed to host kernel.org to deliver long-term stability for the development team.