Sometimes I think I'm pretty hip to the jargon but every once in a while I learn a new one. IoC is an "Indicator of compromise."
This place worse than most, tends to eschew in-jokes and memes as marks of belonging and membership, and rely instead on unexplained jargon.
The unexplained jargon isn't any worse here than anywhere else. Everything from motorcycling to woodworking to sewing has its own arcane terminology for simple concepts to ostracize the unlearned.
Yes, you too can get icy stares from a table full of middle-aged women at the sewing club for failing to be born with the knowledge that "the thing that does edges" is actually called a "serger."
"C-and-C", for "command-and-control," is particularly vague and has multiple presentations-- C+C (Music Factory? An equation?), CnC (machining for materials fabrication), C2 (tutoring? Dicarbons?), C&C (a law firm?), CC (credit card).
APT (advanced persistent threat or Aptitude package manager?) is also annoying.
If you're curious, a whole bunch of security-related acronyms are reflected in the various product names and descriptions here:
It's rough if you're skimming though (and who has time to read everything on the web?)