Give TryHackMe a go
TryHackMe goes way beyond textbooks and focuses on fun interactive lessons that make you put theory into practice. You'll get an immersive learning experience with network simulations, intentionally vulnerable technology based on real world examples and more.
Learn Alloy
Alloy is an open source language and analyzer for software modeling. It has been used in a wide range of applications, from finding holes in security mechanisms to designing telephone switching networks.
Learn hacking skills using HackTheBox
Hack The Box is a massive, online cybersecurity training platform, allowing individuals, companies, universities and all kinds of organizations around the world to level up their hacking skills.
Learn TLA+
TLA+ is a “formal specification language”, a means of designing systems that lets you directly test those designs. Developed by the Turing award-winner Leslie Lamport, TLA+ has been endorsed by companies like AWS, Microsoft, and Crowdstrike.
Try out bWAPP
bWAPP, or a buggy web application, is a free and open source deliberately insecure web application. It helps security enthusiasts, developers and students to discover and to prevent web vulnerabilities. bWAPP prepares one to conduct successful penetration testing and ethical hacking projects. What makes bWAPP so unique? Well, it has over 100 web vulnerabilities! It covers all major known web bugs, including all risks from the OWASP Top 10 project. bWAPP is a PHP application that uses a MySQL database. It can be hosted on Linux/Windows with Apache/IIS and MySQL. It can also be installed with WAMP or XAMPP. Another possibility is to download the bee-box, a custom Linux VM pre-installed with bWAPP.
Try out OWASP Mutillidae II
OWASP Mutillidae II is a free, open-source, deliberately vulnerable web application providing a target for web-security training. With dozens of vulnerabilities and hints to help the user; this is an easy-to-use web hacking environment designed for labs, security enthusiast, classrooms, CTF, and vulnerability assessment tool targets.