So, what's counter-intelligence?

 If you're hanging around the intelligence community, or watching too many spy movies, then sooner or later you're going to hear the term "counter-intelligence". But what is it, and why would you need it?

Simply put, if intelligence is how you find stuff out, then counter-intelligence is how you prevent the other guys from finding out stuff. How do you do that? There are two basic techniques: obfuscation, and increasing the "noise" (if you've ever heard the term "signal-to-noise ratio"). As an aside, and broadly speaking, those are the same two basic techniques used in cryptography.

Obfuscation means hiding what your opponent wants to see. This includes things like fences and barriers to keep prying eyes away from your facilities (blocking HUMINT), covered or underground facilities to foil GEOINT, and encrypting communications to block SIGINT. Classification and control of information also falls under obfuscation, by (hopefully) making it harder for the other people to get the information. By extension, vetting your people before providing them access to that information would also fall here, although it's now stretching the definition of "obfuscate" beyond all reasonable use...

Adding noise means creating additional false data points to force your opponent to spend more time on analysis, and hopefully to draw incorrect conclusions. For example, this might include creating fake military sites or vehicles to fool air reconnaissance. There was a famous (alleged) instance in WWII where the Germans built a fake air field with ersatz planes and equipment manufactured of wood to fool the British, or so they thought. The British waited until the fake facility was completed, then sent over a single plane that dropped a single wooden bomb. (I will note that Snopes rates the anecdote as "unproven".)

Another even more famous example from the same conflict was Operation Mincemeat, in which the British used a deceased homeless man (dressed in a military uniform) to feed false plans to the German intelligence machine. Incredibly, the plan for Operation Mincemeat was conceptualized by none other than Ian Fleming, who would later go on to write the James Bond books.

Picture from Microsoft Word ClipArt