ARPANET TIPs had an obscure but documented low level feature that you could send commands on behalf of other users connected to the same TIP, configuring their terminal settings, disconnecting and reconnecting their sessions to other hosts and ports! You could also execute annoying commands like "@S B" (Send Break) that inserted an ^G into their input stream on ITS, or "@I 33" (Intercept 33 octal) that changed their TIP command intercept character from @ to ESC.

Ostensibly it was so you could configure and control a Teletype or line printer connected directly to a TIP without a modem, but you could also set up TIP-to-TIP links for chatting with other users on different TIPs by bouncing packets directly off a socket without actually logging in to any host!

MIT AI Lab Tourist Policy (why jslabovitz and I were able to get "tourist" accounts at the MIT AI Lab just by asking -- or actually just trying to log in as an unknown user, and automatically being offered our own account!):

https://donhopkins.medium.com/mit-ai-lab-tourist-policy-f73b...

https://news.ycombinator.com/item?id=13518273

jslabovitz on Jan 30, 2017 | parent | context | favorite | on: PDP-10/its: Incompatible Timesharing System

Around 1982, I had an account on MIT-MC, an ITS computer. I was not an MIT student -- rather, a curious teenage hacker from DC. I'd found a text file with 'interesting modem numbers,' and one of those was to a DoD TAC (basically, a dial-in). I recall the text file had a note saying how to connect (via NCP, not TCP/IP) to MIT-MC.

I connected, and remember playing around (as we did) at the login prompt. I probably tried to login as 'guest' or something, and the result was basically, 'There's no user by that name. Do you want an account?' Of course, I said yes -- and shortly received my own account.

Stallman may have been sponsoring logins for folks like myself; he definitely was a little later when I got an account on MIT-AI (or was it MIT-OZ?), which was by that point a TOPS-20 machine.

ITS was a very bizarre system, really with its own social culture. Even in 1982, it felt strangely archaic. The debugger-as-shell was definitely an interesting concept.

Once I accidentally deleted a file. I felt awful, and emailed one of the admins, assuming they'd kick me off. He was like, 'Ah, no worries. We'll just restore it from tape.'

DonHopkins on Jan 30, 2017 | next [–]

NBS TIP: 301-948-3850

I dialed it enough times that I still remember it. Much thanks to Bruce of "Bruce's NorthStar" BBS in Virginia for that phone number. [1]

MIT-MC: @L 236

MIT-AI: @L 134

MIT-DM: @L 70

MIT-ML: @L 198

Anyone remember how to do a TIP-to-TIP link, as documented on page 5-4 of the "Users Guide to the Terminal IMP" [2], by connecting an input and output socket of one TIP to an input and output socket of another TIP, through an unsuspecting host, so you could chat back and forth directly between two TIP dial-ups, without actually logging into the host?

It went something like @HOST #, @SEND TO SOCKET #, @RECEIVE FROM SOCKET #, @PROTOCOL BOTH, making sure the sockets were different parity so as not to violate the Anita Bryant clause with homosocketuality. [3]

You could also add the octal device port number of any other TIP user on your same TIP after the @ and before the command, to execute those commands on their session. (See page 5-7, "Setting Another Terminal's Parameters".) BBN wrote such great documentation and would mail copies of it for free to anyone who asked (that's how I got mine), you couldn't even call it security by obscurity!

The "ARPANET" episode of "The Americans" really missed the boat about how easy it was to break into the ARPANET. I didn't even have to kill anyone! [3] [4] Makes me wonder about the part about squeezing your anus... [5]

What was your uname?

-A2DEH

[1] https://games.slashdot.org/comments.pl?sid=242967&cid=196819...

[2] https://archive.org/details/bitsavers_bbntipADA0eTerminalIMP...

[3] https://news.ycombinator.com/item?id=12422813

[4] https://en.wikipedia.org/wiki/Arpanet_(The_Americans)

[5] https://www.youtube.com/watch?v=hVth6T3gMa0

[6] https://www.youtube.com/watch?v=s3OMSMq9zPA