Yeah. I once worked on a project implementing the software for a fighter aircraft first-line test set - the kind of thing that a maintainer would connect up to the pylons to check out the wiring and make sure the right voltages were getting where they were meant to.

We had to run the whole project on a completely separate network from the rest of the business due to the classification of the software, which was driven entirely by a handful of frequencies used in testing; details of which were also broadly available from OSINT sources.

I feel like there's a joke about Perl hiding somewhere in there.

"There's more than one way to do it, and all of them are classified!" (TIMTOWTDI TS) :)