HackTheBox (https://www.hackthebox.com/ https://www.hackthebox.com/) is the largest and most active hacker challenge website. Focussed mainly around black box p

HackTheBox (https://www.hackthebox.com/ https://www.hackthebox.com/) is the largest and most active hacker challenge website. Focussed mainly around black box pentesting of vulnerable Windows and Linux machines, but they have lots of other types of content these days too such as CTF challenges and paid lab environments.