Maybe Donald Trump is an aficionado of weird sexual practices, and maybe not: I really have no way of knowing. But I do know that stories of precisely this sort are a very common tactic used by intelligence agencies to discredit political figures at all levels. With very little effort, I can also tell you exactly how such tales emerge and how they fit into the modus operandi of particular agencies and governments, and there is no excuse whatever for other people not to know this.

The fact that U.S. agencies and media are being so uncritical of these latest Trump exposés and “dossiers” is alarming. The whole affair should alert us to the wave of bogus stories we can expect to be polluting our public life in the next few years.

Since so many roads in this affair seem to lead back to Russia, some background might be helpful. In 1991, senior KGB officer Vasili Mitrokhin defected to the British, carrying with him an amazing haul of secret documents and internal archives. Working with respected intelligence historian Christopher Andrew, Mitrokhin published a number of well-received books, including The Sword and the Shield (1999). The Mitrokhin Archive demonstrates the vast scale of Soviet disinformation—the invention and circulation of stories that were untrue or wildly exaggerated, commonly with a view to discredit critics or opponents of the USSR. These functions were the work of the KGB’s Service A, which was superlative at planting stories around the world, commonly using out-of-the-way news media. Service A also did a magnificent job of forging documents to support their tall tales. (Even serious and skeptical historians long accepted the authenticity of a particularly brilliant forged letter notionally sent by Lee Harvey Oswald.) Such disinformation was a major part of the KGB’s functions during the 1970s and 1980s, which were the formative years of the up-and-coming young KGB officer, Vladimir Putin.

One instance in particular illustrates Service A’s methods and how triumphantly they could shape public opinion. The Soviets naturally wanted to destroy the reputation of FBI Director J. Edgar Hoover, a dedicated and lethally effective foe of Soviet espionage until his death in 1972. Even after his death, the vilification continued, and in the context of the time, the deadliest charge that could be levied against him was that of homosexuality. Accordingly, the Mitrokhin Archive shows how hard the Soviets worked to spread that rumor.

Now, Hoover’s real sexual tendencies are not clear. He was a lifelong bachelor who maintained a very close friendship with a male subordinate, and our modern expectations would be that he was a closeted homosexual. Having said that, during Hoover’s youth it was common for members of the same gender to share close non-sexual friendships. What we can say with total confidence is that Hoover was fanatically conscious of his privacy and security, to the point of paranoia, and there was no way that he would do anything public that could arouse scandal or permit blackmail.

That context must make us very suspicious indeed of claims that Hoover was not only homosexual, but also a transvestite, stories that have become deeply entrenched in popular culture. But the origins of the cross-dressing stories are very suspect. The only source commonly quoted is a 1991 affidavit by a woman who claimed that some decades earlier she had met a heavily dragged-up Hoover at a private event, where he allegedly wished to be addressed as “Mary.” The story is multiply improbable, most would say incredible, and has been rejected even by historians who normally have nothing good to say about Hoover. Yet the tale circulated widely, and wildly. In 1993, searching for a new head of the FBI, the ever-tasteful new president Bill Clinton joked that it would be hard to find someone to fill Hoover’s pumps.

We can’t prove that Service A invented or spread the specific cross-dressing stories about Hoover, but they fit exactly with other Soviet efforts through the 1970s and 1980s. And that legend has subsequently become a truth universally acknowledged.

The Russians were absolutely not the only agency that circulated disinformation. Such tactics are common to most major agencies, including those of the U.S. But looking at the recent Trump revelations, we constantly encounter Russian sources for scabrous tales that are about as improbable as that of “Mary” Hoover.

The Trump dossier that is the source of current attention might be accurate, but there are real grounds for suspicion. The main source is a respected and credible British private agency, which like most organizations of its kind draws heavily on former members of that nation’s mainstream intelligence service. But this particular dossier was evidently not compiled by the standard means used by such agencies, where competing sources are evaluated and judged in an adversarial process. (Team A makes the best case for one interpretation, Team B argues the opposite, and you see which side makes the most credible argument.) Rather, the Trump material was gathered on a parti pris basis with the specific goal of collecting negative information on the then-candidate. This is in consequence a partisan report, which just did not exercise the kind of skepticism you would expect in a normal intelligence analysis. The stories (including the one involving the fetish) look not so much like kompromat (compromising material, which might be true) but rather seem to be Russian dezinformatsiya, disinformation.

I was stunned to read a recent story in the British Guardian suggesting that the CIA and FBI had “taken various factors into consideration before deciding [the dossier] had credibility. They include Trump’s public comments during the campaign, when he urged Russia to hack Hillary Clinton’s emails.” Is there really anyone who did not hear that “urging” as a classically outrageous Trumpian joke? Yet that is here cited as major confirmation of his sinister Russian connections.

Why would the Russians create such material, if it might discredit a figure who actually promised to be a close ally on the global stage? Perhaps it was a kind of insurance, to keep Trump in line if he became too hostile to future Putin actions. Far more likely, it was part of a general series of stories, scares, myths, and downright falsehoods that have circulated so freely over the past 18 months, with the collective goal of discrediting the U.S. democratic system and fomenting dissension, paranoia, and outright hatred in American public life. The Russians control our elections! The Russians watch everything you say and write, no matter how private you think it is! Russian hackers gave the Rust Belt states to Trump! Trump is a Putin puppet!

If the Russians were seeking to undermine the American political order, to discredit the U.S. presidency, and in short to destabilize the United States, then they have succeeded magnificently in their goal.

Over the next few years, Donald Trump’s many critics will be very open to accepting any and all wild stories about him and his circle. Some of those rumors might even be true. But a great many will be disinformation stories spread by the Russians and, who knows, by other international mischief makers. It would be wise to exercise some caution before falling for the next tall tale.

Philip Jenkins is the author of The Many Faces of Christ: The Thousand Year Story of the Survival and Influence of the Lost Gospels. He is distinguished professor of history at Baylor University and serves as co-director for the Program on Historical Studies of Religion in the Institute for Studies of Religion.