HackTheBox is probably the most widely-known platform for Capture The Flag challenges, featuring a fully-managed network of vulnerable systems. They offer both free and paid services. The free service provides access to all currently-active challenges, while the paid service provides additional access to all retired challenges, as well as lower-latency connections to the VPN.
As per the Terms of Service, walk-throughs are not allowed to be published for currently-active machines. Therefore, the following walk-throughs focus on retired machines.
To gain access to these retired machines, you’ll need a VIP account on HackTheBox. VIP accounts are not free, but they are not prohibitively expensive, and offer many advantages over the free account.
Creating an account on HackTheBox is a little more complicated than on most websites, as they require you to hack their sign-up process. We urge you to attempt to solve this puzzle on your own, but if you struggle with this step, there are numerous guides on the internet for how to hack the sign-up process. Remember: Google is your greatest asset!