If you are interested in penetration testing (pentesting), digital forensics, and in playing with software applications that hackers use on a daily basis, there are several Linux distributions that make those applications readily available.
These are niche or specialty distributions that have been packaged with all the Free Software applications that the best in the business use, and that anybody with a computer can download and install.
There are just a handful of these distributions and all have had at least one article about them published on this website. In alphabetical order, they are:
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