Tails is a portable operating system that protects against surveillance and censorship.
The Fedora Security Lab provides a safe test environment to work on security auditing, forensics, system rescue and teaching security testing methodologies in universities and other organizations.
Qubes is a security-oriented, free and open-source operating system for personal computers that allows you to securely compartmentalize your digital life.
Home of Kali Linux, an Advanced Penetration Testing Linux distribution used for Penetration Testing, Ethical Hacking and network security assessments.