Kali Linux:
Developed by Offensive Security as the rewrite of BackTrack, Kali Linux distro tops our list of the best operating systems for hacking purposes. This Debian-based OS comes with 600+ preinstalled pen testing tools that make your security toolbox richer. These versatile tools are updated regularly and are available for different platforms like ARM and VMware. For a forensic job, this top hacking operating system comes with a live boot capability that provides a perfect environment for vulnerability detection. Now Kali Linux is based on a rolling release model
https://www.kali.org/downloads/
Parrot Security OS:
Debian-based Parrot Security OS is developed by Frozenbox’s team. This cloud-friendly Linux distribution is designed for ethical hacking, pen testing, computer forensics, ethical hacking, cryptography etc. Compared to others, Parrot Security OS promises a lightweight OS that is highly efficient. Along with its plethora of legally recognized tools, you also get the opportunity to work and surf anonymously.
For those who don’t know, Parrot Security OS is a mixture of Frozenbox OS and Kali Linux. The OS uses Kali repos for updating its tools, but it has its own dedicated repo for storing the custom packets. It comes with MATE desktop environment and the powerful interface is derived from famous Gnome 2. This highly customizable hacking oeprating system also comes with a strong community support.
https://www.parrotsec.org/download/
BackBox:
BackBox Linux is an Ubuntu-based operating system with its focus on security assessment and penetration testing. BackBox Linux comes with a wide range of security analysis tools that help you in web application analysis, network analysis etc. This fast and easy to use hackers’ favorite Linux distro comes with a complete desktop environment. The software repos of the hacking tools in this hacking operating system are regularly updated with the most stable versions.
Samurai Web Testing Framework:
Samurai Web Testing Framework is basically a live Linux environment that comes pre-configured to work as a web pen-testing platform. The framework contains multiple free and open source hacking tools for detecting vulnerabilities in websites. It’s often called the best operating system for Web Penetration Testing.
http://sourceforge.net/projects/samurai/files/
Pentoo Linux:
Based on Gentoo Linux, Pentoo is a pen testing operating system that is available as a 32 and 64-bit installable Live CD. You can also use Pentoo on top of an existing Gentoo Linux installation. This XFCE-based distro comes with persistence support that allows you to save all the changes you make before running off a USB stick.
This excellent hacking operating system comes with a wide variety of tools that fall under categories like Exploit, Cracker, Database, Scanner etc. This Gentoo derivative inherits the Gentoo Hardened feature set that brings additional control and configuration.
http://www.pentoo.ch/download/
BlackArch Linux:
BlackArch Linux is available as a complete Linux distribution for security researchers and ethical hackers. It’s derived from Arch Linux and one can also install the BlackArch Linux components on top of it.
The constantly growing repo of this useful operating system for hacking purposes is stuffed with more than 1400 tools that are thoroughly tested before being added to the codebase.
http://blackarch.org/downloads.html
Bugtraq:
Available in Debian, Ubuntu, and OpenSuSe, Bugtraq is famous for its electronic mailing list that is purely dedicated to computer security. The issues that are covered are vulnerability discussion, security-related announcements, exploitation methods etc. The Bugtraq Team consists of experienced hackers and developers that offer a great service for ethicals and pen testers.
Bugtraq comes with tons of pen testing tools including mobile forensic tools, malware testing tools and other software developed by the Bugtraq-Community.