JargonFile/entries/OS and JEDGAR.txt

OS and JEDGAR

This story says a lot about the ITS ethos. On the ITS system there was a
program that allowed you to see what was being printed on someone else's
terminal. It spied on the other guy's output by examining the insides of the
monitor system. The output spy program was called OS. Throughout the rest of
the computer science world (and at IBM too) OS means operating system, but
among old-time ITS hackers it almost always meant output spy. OS could work
because ITS purposely had very little in the way of protection that
prevented one user from trespassing on another's areas. Fair is fair,
however. There was another program that would automatically notify you if
anyone started to spy on your output. It worked in exactly the same way, by
looking at the insides of the operating system to see if anyone else was
looking at the insides that had to do with your output. This counterspy
program was called JEDGAR (a six-letterism pronounced as two syllables:
/jedgr/ ), in honor of the former head of the FBI. But there's more. JEDGAR
would ask the user for license to kill. If the user said yes, then JEDGAR
would actually gun the job of the luser who was spying. Unfortunately,
people found that this made life too violent, especially when tourists
learned about it. One of the systems hackers solved the problem by replacing
JEDGAR with another program that only pretended to do its job. It took a
long time to do this, because every copy of JEDGAR had to be patched. To
this day no one knows how many people never figured out that JEDGAR had been
defanged. Interestingly, there is still a security module named JEDGAR alive
as of late 1999  in the Unisys MCP for large systems. It is unknown to us
whether the name is tribute or independent invention.