[willvarfar]

Traffic Analysis.

A lot of British intelligence during WW2 was gleamed not from the contents of the messages they intercepted, but rather from tracking who was where and communicating with whom.

And if you stop soldiers from using mobile phones on restricted ground, you are just going to have lots of tracks stopping abruptly at the gates and secure facilities identifiable by their lack of emissions.

Patterns.

There have been great examples of correctly identifying the crews of nuclear submarines by their predictable periods of time offline.

[stan_rogers]

It was giving that away in his book, rather than any of the other activities at Bletchley Park, that got Gordon Welchman into trouble. Even without any detail as to the techniques used, the fact that he and his group had basically worked out the German operational structure and deployment situation entirely from traffic analysis before the improved Enigma was reliably broken revealed a lot that was meant to be kept secret.

[willvarfar]

Yes the hut six story was an excellent and eye opening book. We are quick to idolize Turing - and he was an amazing man - but there are others such as Welchman and Tutte who sadly get less attention.

[sitkack]

In fact, if I were running strategy, I would want my opponent to think I used a computer of speed x or storage system of size k, spending lots of resources chasing a false solution.

[SiempreViernes]

Just make the exclusion region a bit bigger than the grounds itself?

In any case, the attack here was to identify personnel based on known locations, not finding new locations in the first place. Big bases can't be hidden anyway, the best you can do is conceal what happens indoor in them so it seems silly to let foreign intelligence track personnel movement inside a base...