■■■□□ CTF Challenges.
Hacker101 CTF: Free hacking courses & challenges (hacker101.com/ctf)
VulnHub: Download vulnerable VMs to hack offline (vulnhub.com)
OverTheWire: Wargames for all levels, start with Bandit (overthewire.org)
CTFLearn: Beginner-friendly CTF challenges (ctflearn.com)
picoCTF (https://picoctf.org/)
RingZer0 CTF: Tons of fun challenges (ringzer0ctf.com)
Bugcrowd University: Open-source hacking training (university.bugcrowd.com)
UnderTheWire: PowerShell-based wargames (underthewire.tech)