The Ansible Hardening role from the OpenStack project is a great way to secure Linux boxes in a reliable, repeatable and customisable manner.
It was created by former colleague of mine Major Hayden and while it was spun out of OpenStack, it can be applied generally to a number of the major Linux distros (including Fedora, RHEL, CentOS, Debian, SUSE).
The role is based on the Secure Technical Implementation Guide (STIG) out of the Unites States for RHEL, which provides recommendations on how best to secure a host and the services it runs (category one for highly sensitive systems, two for medium and three for low). This is similar to the Information Security Manual (ISM) we have in Australia, although the STIG is more explicit.
Firefox has (unfortunately) lagged behind other browsers recently when it comes to implementing the more secure TLS 1.2 and it’s only now officially landing in the upcoming release 27. It can always use more testing though and if you’re running version 26 you can still enable it and test.
Set the following:
This is the maximum supported protocol so it doesn’t mean that the sites you visit will now be using TLS 1.2. If you want to (try and) force it, there is a security.tls.version.min but be warned that probably most of your sites will fail.
You may also wish to disable this deprecated SSL3 algorithm:
You can test this out by browsing to http://howsmyssl.com.
Calomel is a handy addon (BSD licence) to tell you what your secure connection negotiated to when you visit a site and gives it a score.
If you notice breakage, please report upstream.
Came across a decent collection of tips for SSH by Vivek Gite. If you’re using SSH (and even if you’re not!) it’s worth a look.