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
-
There's a New Linux AI Assistant in Town
Newelle is a Linux AI assistant that can work with different LLMs and includes document parsing and profiles.
-
Linux Kernel 6.16 Released with Minor Fixes
The latest Linux kernel doesn't really include any big-ticket features, just a lot of lines of code.
-
EU Sovereign Tech Fund Gains Traction
OpenForum Europe recently released a report regarding a sovereign tech fund with backing from several significant entities.
-
FreeBSD Promises a Full Desktop Installer
FreeBSD has lacked an option to include a full desktop environment during installation.
-
Linux Hits an Important Milestone
If you pay attention to the news in the Linux-sphere, you've probably heard that the open source operating system recently crashed through a ceiling no one thought possible.
-
Plasma Bigscreen Returns
A developer discovered that the Plasma Bigscreen feature had been sitting untouched, so he decided to do something about it.
-
CachyOS Now Lets Users Choose Their Shell
Imagine getting the opportunity to select which shell you want during the installation of your favorite Linux distribution. That's now a thing.
-
Wayland 1.24 Released with Fixes and New Features
Wayland continues to move forward, while X11 slowly vanishes into the shadows, and the latest release includes plenty of improvements.
-
Bugs Found in sudo
Two critical flaws allow users to gain access to root privileges.
-
Fedora Continues 32-Bit Support
In a move that should come as a relief to some portions of the Linux community, Fedora will continue supporting 32-bit architecture.