Deprive the Soviets of toilet paper.
At some point during the US/Soviet power struggle, the United States and its allies realized that they were able to obtain Soviet garbage pretty easily, especially in and around (then East) Germany. In general, though, trash is just that — trash — and lacks any sort of value, especially to someone looking for information. After all, Soviets aren’t going to simply throw out a confidential document (and, knowing this, aren’t likely to care what happens to the stuff in garbage). The Western powers had an opportunity, though — if they could somehow induce the Soviets to throw classified documents into the garbage, more information could be recovered. Enter Operation Tamarisk.
By depriving the Russians of toilet paper, the theory went, the soldiers etc. would have to wipe with something else. There typically were not a lot of options, so many just used an official document or two sitting idly by. And because these documents weren’t water soluble, they also weren’t flushable — at all. The Russians would wipe and toss the classified document-turned-toilet paper into a nearby garbage can. And that’s where the Western spies came into action. By searching through trash.
What they found there, of course, was more than just secret documents (covered in “stuff” or otherwise) detailing the covert operations of the Soviet military industrial complex. As Wikipedia notes, the Western counterintelligence agents found much more than paper and feces. They also found amputated limbs among the trash and, when they complained to their superiors, their superiors took action. But instead of calling the mission off, they ordered the agents to dig further, and investigate the types of shrapnel the Soviets were using.
Despite the gore and overall grossness, the plan was a success — often considered one of the most successful intelligence missions of the Cold War.
Bonus fact: In general, intelligence agencies destroy classified documents as necessary — that’s where the term “burn after reading” comes from. The CIA does exactly that, and does so in a way to also conserve energy. According to TPM, the exhaust from the incinerator used to burn the documents is used to heat water at headquarters.
From the Archives: Pig Toilets: Where the people do their business, pigs play and eat.
Related: Emergency toilet paper.