I just stumbled across some notes I’d made from back when I had a bit of a play with this. There’s a whole (fake) Arpanet in there to explore, and exploits to find and deploy, and badges to collect, modems and usenet:
$ telnet telehack.com
Apparently you can play it from your Z88, if you have your Z88 connected to today’s internet…
Here’s an Interview with Telehack’s Anonymous Creator under the heading Playable Archaeology.
Whether you miss the good old days of Telnet or you want to know what hacking was like when security was nothing but an afterthought, Telehack is the game for you. The text-based hacking game is a simulation of a stylized combination of ARPANET and Usenet, circa 1985 to 1990, with a full multi-user universe and player interactions, including 26,600 hosts.
There are hints and tips here: