What is the recommended security software for Linux?

I have QubesOS environment. (QubesOS is an OS that can be run by using Xen’s virtual machine technology, recommended by Edward Snowden.) TemplateOS used is Debian, Fedora, Whonix. The question is, I want to improve security and privacy, so I would like to install security software. Is there any good software? What you need is both open source and free. Also, please let me know if there are other security and privacy measures you are taking! !

Tor browser comes to mind. Various firefox extensions for web browsing when not using tor. When it comes to the system there’s good firewall setup, VPN’s etc.

I’ve never had any luck configuring QubeOS to even allow my internet USB key to work, and since i also use my main computer for audiovisual work and gaming, the way GPU’s are handled in VM’s made it not worth my time for my personal case. (And the ram limit was too high for my netbook but this was expected)

So, those are habitually what i use on more “conventional” linux distros. Due to the particular manner of QubesOS i don’t know if those are useful, or even can be applied at all.

grapheneX: https://graphenex.github.io
A python script making easier to harden your computer security trought its use of custom modules. Also have a web local UI if you are scared of the terminal.

kloak: https://github.com/vmonaco/kloak
A privacy tool that makes keystroke biometrics less effective. This is accomplished by obfuscating the time intervals between key press and release events, which are typically used for identification.

hblock: https://github.com/hectorm/hblock
Improve your security and privacy by blocking ads, tracking and malware domains trought the use of your host file. Automatise a well maintain host file.

Thank you for the wonderful explanation! ! I want to hear more details. I want to listen to your PC OS, mobile OS, software, provider, etc! !

Well, I didn’t say those since those aren’t that privacy or security focused, at the exception to my smartphone OS and my laptop OS.

Main PC OS (Work/Gaming OS) : deepin 15.11 https://www.deepin.org/en
deepin (formerly, Deepin, Linux Deepin, Hiweed GNU/Linux) is a Debian-based distribution that aims to provide an elegant, user-friendly and reliable operating system. It does not only include the best the open source world has to offer, but it has also created its own desktop environment called DDE or Deepin Desktop Environment which is based on the Qt 5 toolkit. Deepin focuses much of its attention on intuitive design.

Laptop OS: KodachiOS https://www.digi77.com/linux-kodachi
Linux Kodachi is a Debian-based distribution which can be run from a DVD or USB thumb drive. The distribution filters all network traffic through a VPN and the Tor network, obscuring the user’s network location. The distribution attempts to clean up after itself, removing traces of its use from the computer.

MobileOS currently : /e/ (or eelo) https://e.foundation
French LineageOS fork which aims to create a complete and beginner friendly system, without any remaining Google bits, while still making it usable for the user with its privacy open-source incorporated apps.

Upcoming MobileOS: PureOS (Coming with the Librem5) https://puri.sm/products/librem-5/pureos-mobile
PureOS is a GNU/Linux distribution based on Debian. It is a desktop distribution that can be used as full-featured operating system as installed as a mobile OS or a desktop OS. PureOS uses free and open source software exclusively and is endorsed by the Free Software Foundation.

How about QubesOS and GrapheneOS? These were also valued by Snowden. Also, isn’t it dangerous because PureOS is not open source?

Read my message more carefully. Especially the first sentence.
Also, PureOS is open source. https://repo.pureos.net/pureos/pool/main/