You wouldn't believe the hoops I had to jump through to get that thing working - it had to be in my apartment at the time since the office phone systems were too modern, and connecting a (borrowed) vintage US Robotics Sportster 2400 (from 1987!) up to a vaguely modern Linux PC involved tomfoolery with various adaptors. USB to RS-232, DB-9 then DB-9 to DB-25.
System had mgetty listening to the modem, doing appropriate line control stuff - when people connected and entered the username 'backup', it would fling them straight into a hacked-together PHP script (stop laughing!) which asked for a password and then cycled through various plot fragments and home-made ANSI-art conversions of Portal 2 imagery, before kicking them off after a few minutes. (Why did the script itself ask for the password? I'd discovered a bit too late that the 'backup' user was Quite Important in Debian, and instead had to find an mgetty work-around. Which had the interesting effect that if you failed to type in 'backup' in the first login attempt on that connection, subsequent attempts would be tested against the real, no-login-available 'backup' user. Which actually delayed people's successful logins for quarter of an hour or so, since someone had failed a login with the correct username and password that way. Wahey!)
Testing was fun with only one phone line. I had a 'local' version running, with two modems attached together by a short phone cable - but this needed poking at mgetting with various signals to get it to pick up the line. With the BBS modem actually connected to the real phone line, I could call in with my mobile phone, and verify that it would automatically pick up and started squeaking. But knowing that the modem could actually send and receive data over the real phone line? Blinking heck completely untested!
Phone was ringing off the hook for over a week. I have no idea what the phone company thought I was doing - with this newly set-up phone line constantly receiving calls from all over the world...
I saw forum posts wondering what size datacentre we'd set up for this thing. Um....
Video of the thing in action here - PC doing all the work, Mac laptop logged into the logging stuff over SSH.
Recent Eurogamer article here!