The modern era of the Internet has given us a seemingly never-ending bounty of farfetched conspiracy theories. Some of the loudest of those fringe movements have become pervasive enough and serious enough to qualify as domestic terror threats, the FBI says.

Yahoo News today published an internal FBI document it obtained warning of "conspiracy-theory-driven domestic extremists."

The memo, dated May 30, describes "anti-government, identity-based, and fringe political conspiracy theories" as likely to motivate extremists "to commit criminal or violent activity."

In the memo, the FBI says the document is the first bureau product to explicitly discuss the future threat from domestic extremists driven by modern conspiracy theories.

Conspiracy theories of some kind or another are nearly as old as communication itself, but the always-online era has accelerated their growth and broadened their spread.

"Although conspiracy theory-driven crime and violence is not a new phenomenon," the memo continues, "Today's information environment has changed the way conspiracy theories develop, spread, and evolve."

In the FBI's assessment, the bureau warns, these conspiracy movements "very likely will emerge, spread, and evolve in the modern information marketplace over the near term, fostering anti-government sentiment, promoting racial and religious prejudice, increasing political tensions, and occasionally driving both groups and individuals to commit criminal or violent acts," especially as we move into the 2020 election season.

The FBI, later in the document, defines "very likely" as a greater than 80% chance of something occurring.

Not just a hypothetical

The memo explicitly cites both Pizzagate and QAnon as examples of modern "fringe political" conspiracy theories that have already been implicated in violence.

The "Pizzagate" theory came to a head in 2016, when a devotee marched into a DC pizzeria with an AR-15 and started making threats.

The theory claimed—falsely—that high-ranking Democratic Party officials were operating a child sex ring out of the basement of the pizza shop, which received hundreds of threats. The shooter took it upon himself to "self-investigate" and was ultimately sentenced to four years in prison on weapons and assault charges.

The assault on the pizzeria did not stop the conspiracists. As recently as December, the FBI memo says, an individual found in possession of bomb-making materials said he was going to blow up a monument in Springfield, Illinois, "to make Americans aware of Pizzagate" and other conspiracies.

QAnon, meanwhile, is complicated enough that its own adherents can sometimes barely follow all its ins and outs. In broad strokes, QAnon posits that an anonymous insider known as "Q" is constantly dripping out insider information about Donald Trump's byzantine, long-term plans to take down the "deep state."

Although still a fringe belief, some right-wing celebrities and pundits have embraced the conspiracy and lent more credence to its followers. These enthusiasts subsequently show up at Trump rallies and draw positive attention from the president.

In June 2018, a Nevada man used an armored truck to block all traffic next to the Hoover Dam. The man, who was found to have several weapons inside his vehicle, "referenced the QAnon conspiracy theory directly and discussed related conspiratorial beliefs after his arrest," the FBI memo says.

That incident came only a few weeks after a different man claimed a homeless camp in Arizona was actually the site of child trafficking. After law enforcement came to investigate and found nothing, he "repeatedly alleged a law enforcement cover-up and referenced the QAnon conspiracy theory as he and armed group members searched for additional camps" and engaged in "criminal activities," according to the memo.

A former Department of Homeland Security counterterrorism official told Yahoo News that while the threat may be real, it seems unlikely to be mitigated any time soon. "Nearly all, if not all, the intelligence analysts focusing on domestic extremist groups" at DHS have left or been put out of work during the Trump administration, he told Yahoo. "There is no one there" to do the work to investigate or stop it.

The FBI, for its part, told Yahoo News in a statement that it can "never initiate an investigation based solely on First Amendment protected activity. As with all of our investigations, the FBI can never monitor a website or a social media platform without probable cause."

Another right-wing conspiracy theory, related to the 2016 killing of Democratic National Committee staffer Seth Rich, was recently reported to be the work of Russian intelligence.