Workshop: Lock down your Linux system with Firewalld and OpenSnitch

Double Protection

© Lead Image courtesy of Sofia Tolstaya, the author's 10-year-old daughter

© Lead Image courtesy of Sofia Tolstaya, the author's 10-year-old daughter

Article from Issue 232/2020

For maximum security, you'd better watch traffic in both directions. This hands-on workshop takes you through the steps of setting up firewalls for outgoing as well as incoming traffic.

Linux has a great selection of firewalls for securing stand-alone computers or whole networks. Small LANs usually depend on small routers for security. But what if your Linux machine is exposed on the network and you don't have control over the upstream router or gateway? What if you're working behind one of the millions of smaller routers with out-of-date firmware or missing security patches?

If you're really serious about building a perfectly secure, network-attached Linux workstation, you'll need to fortify the system from two directions: with a host-based firewall for managing incoming connections and with a per-application firewall for controlling outbound traffic. This hands-on workshop will show you how to fortify your system using Firewalld and the OpenSnitch application firewall.

Limiting the Incoming Flow

Network security starts with limiting access to your host from the outer world. One of the most advanced and popular tools for limiting incoming traffic is Firewalld [1], a modern and flexible firewall that replaced the legacy Iptables software a few years ago. Firewalld was introduced as a default network security solution in Fedora 18 and RHEL 7, and consequently, in CentOS 7 as well. The Firewalld firewall is now included in many other mainstream Linux distributions, such as openSUSE and Arch.


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