Well, not a spy per se but my dad worked for IBM beginning in the mid ‘60s and we spent several years in Japan. My dad had a title that indicated he was in sales, BUT what the fuck is a computer sales person doing going to places like Truk and Palau and Saigon in the middle of a shootin’ war? Took me a weirdly long time to put together how unlikely it all was, including the fact that we lived off base but my dependent’s military ID listed dad’s rank as GS-15, which is ludicrously high for a sales person selling computers in a war zone working for a company that at the time was about 98% a defense contractor. I recently had it confirmed by my mom that he also had a top secret clearance in the Air Force, a higher clearance when we were in Japan and that she herself held a high level clearance dating back to before they married, as she was working for Martin (later Lockheed-Martin) on a missile contract. So yeah, apparently my parents were just a bit more than they appeared to be. 
That doesn’t necessarily signify “spy” - my job required background checks for my security clearance and all I did was sit in a cubicle reading stuff and writing stuff about what I’d read. Similarly when I was in the Navy, since the job would expose me to classified material, I needed a background check to ensure I could be trusted.
Military liaison/observer duty? Like the sort of thing Major Arthur Nicholson was doing before he got killed?
As to the OP, I’ve only met a few overt intelligence personnel. Most were giving lectures on their former work in the 60s and 70s. It sounded like a big pain in the ass, mostly. They couldn’t tell people what they did for a living. Some of them moved around like they were military families, which had to be rough. Paperwork and vetting sounded annoying. But they universally sounded proud of what they did, and acted like they had a job that paid more than juse salary or benefits. Go them.
Could be something like that. There was no way I could verify what he said about is actual mission, but he had the military ID, and I picked him up at the airport one time and he was carrying a diplomatic pouch. He was coming in from Honduras, you can take a guess what he was carrying into the country in that pouch besides official documents. This was the early 80s, DEA couldn’t touch those pouches back then.
There’s a great bit in Charlie Wilson’s War about the grizzled CIA officer Gust, showing his displeasure with some annoying, fresh from the Ivy League, observer or the like, by having Gust’s underlings take the observer to every street food vendor in Peshawar (IIRC EDIT, or maybe it was Cairo?). ‘Get him sick’ was more or less the order. Gust and his cohorts had cast-iron stomachs and either didn’t get ‘Delhi Belly’, or knew how to avoid it.
As I understand it people with classified backgrounds can apply for “rollback”, which allows them to talk (most likely in a limited way) about what they did. It’s a big thing for people who want to leave the government and work elsewhere; otherwise your resume is going to be pretty severely lacking.
I meant a cover story to tell people while you’re still employed as a spy, say at Thanksgiving dinner with your extended family or when you meet someone you went to college with.
I had a neighbor who was a little suspect at times. Traveled often, but would only say “South America”, refused to specify the country. He had a strange habit of never speaking certain words, too. Like “apron” or “swingset”, he’d pretend not to remember the word, but even if reminded, he’d still talk around it.
To be fair, given the choice, you might not eat some of the street food either, like at a place where they take the bowl used by the previous customer, swish it around in a barrel of dirty water, dry it off with some newspaper, and serve you in that. Not all places are, or were, like that, but not all of them would pass even a lax health inspection either. A grizzled spy might indeed know which places to avoid, or have a cast-iron stomach, as you say.
I used to know a genuine Communist who worked for the CIA. The guy was from East Germany.
There was this girl that I thought was a spy. She had eyes like Bette Davis.
Can we joke?
Do Stasi informers count? I met a couple of them as a kid. My family hosted several East German academics who traveled to the US for conferences at my dad’s university. Two of them showed up in his Stasi file. Nice folks, as I recall.
Similar situation with pre-Detente visitors from the USSR. They were supposed to be government and business representatives but after the fall their KGB associations were confirmed. They probably had to be well trusted by the KGB to be allowed out of the country in the first place.
We did a sales call at NSA in Ft. Meade once. The sales guy asked for business cards - they just laughed at him.
If you ask an NSA guy where they work, they’ll say Department of Defense.
Glomar response.
I like to twist cliches around, such as, “If I killed you, I’d have to tell you.”
We were friends with a woman at one of our embassy postings who was a CIA employee. She was an administrative person who was declared to the host government. She was about the farthest thing from a spy as one can get in the CIA, but she loved to hint that she was more than she was. When we were all back in DC at the same time, I called Langley to try to find her. They of course wouldn’t give out any information, but passed my message to her at the school she was attending. She then called me and told me that I’d “blown her cover”. 
My next-door neighbor is an American mercenary, who works for the Iraqi government as a paramilitary. Probably a lot of spying going on there, too.
Well, maybe. Again in the “not-spy-per-se” category. According to a couple of elderly professors of mine (since passed on), apparently back in the day ( like the late 1950’s - 1960’s when Africa in particular was decolonizing) the CIA was happy to occasionally throw a little extra cash towards receptive field scientists working in Third World countries for basic humint. Post-field work debriefing of heard political gossip, that sort of thing.
I got the distinct impression that a couple of these old gentleman-adventurer types I knew may have taken that deal on occasion. It was broadly hinted at with a wink and a nod. But they were always cagey even when trying to impress young undergrads, so who knows how much was bullshit 
.