The Moscow rules are rules-of-thumb said to have been developed during the Cold War to be used by spies and others working in Moscow. The rules are associated with Moscow because the city developed a reputation as being a particularly harsh locale for clandestine operatives who were exposed. The list may never have existed as written.
Although no one had written them down, they were the precepts we all understood for conducting operations in the most difficult of operating environments: the Soviet capital. By the time they got to Moscow, everyone knew these rules. They were dead simple and full of common sense.
There is no limit to a human being's ability to rationalize the truth.
Technology will always let you down.
Once is happenstance. Twice is coincidence. The third time it’s enemy action.
Do not attract attention, even by being overly careful.
Moscow rules are prominently referenced in John le Carré's cold war books including Tinker, Tailor, Soldier, Spy and Smiley's People, as tradecraft, including use of inconspicuous signal markers, the use of dead drops, and the ways to signal the need for a face-to-face meeting. Moscow Rules are important at the beginning of Smiley's People, where the General invokes the rules to request a meeting with Smiley, but he is followed and killed by KGB assassins before it can happen. The applicable rule states that no documents may be carried that cannot be instantly discarded, in this instance a 35mm negative concealed in an empty pack of cigarettes. In Spooks there are references to the Moscow Rules. In particular, in Season 6 Episode 10, Harry Pearce tells someone, "Treat London as enemy territory, keep your head down, find an opportunity, and make a move." In an earlier episode in Season 5, rogue MI6 agent Richard Dempsey is said to be in disguise and following the Moscow Rules, where the idea of treating the place as enemy territory is repeated. Mick Herron's Slough House series refers to the Moscow Rules and counters those with The London Rules. Daniel Silva's Moscow Rules places Gabriel Allon in Moscow. In The Middleman, episode 8, the Moscow Rules are recited. The rules are also referred to briefly by character Leila in the “Too Much Information” chapter of Jonathan Franzen’s novel Purity.