I know there used to be a “web-based game” for practising hacking which actually was a server with certain amounts (of now quite outdated) protection to practice your hacking on. Taking it fully offline or overloading so it was completely unresponsive was frowned upon and there was a warning that your IP would be logged and anybody doing as such should beware.
No idea if it still exists or what the URL was as I didn’t personally have a clue about that kind of thing though…
Back in the day I made a “hacker simulation game” for the C=64 in Basic(!!). You were supposed to hack into a radiostation and take over the broadcast. Pretty crappy when I think about it now, but I thought it was quite cool when I made it. dreamsigh