An anti-government movement that advocates for a violent uprising targeting liberal political opponents and law enforcement has moved from the fringes of the internet into the mainstream and surged on social media in recent months, according to a group of researchers that tracks hate groups.

The movement, which says it wants a second Civil War organized around the term "boogaloo," includes groups on mainstream internet platforms such as Facebook, Instagram, Twitter and Reddit, as well as fringe websites including 4chan, according to a report released Tuesday night by the Network Contagion Research Institute (NCRI), an independent nonprofit of scientists and engineers that tracks and reports on misinformation and hate speech across social media.

While calls for organized and targeted violence in the form of a new Civil War have previously circulated among some hate groups, the emergence of the term "boogaloo" appeared to be a new and discrete movement. NCRI researchers who analyzed more than 100 million social media posts and comments found that through the use of memes — inside jokes commonly in the form of images — extremists have pushed anti-government and anti-law enforcement messages across social media platforms. They have also organized online communities with tens of thousands of members, some of whom have assembled at real-world events.

The report "represents a breakthrough case study in the capacity to identify cyber swarms and viral insurgencies in nearly real time as they are developing in plain sight," John Farmer, a former New Jersey attorney general who is director of the Miller Center for Community Protection and Resilience at Rutgers University, wrote in the report's foreword.

A patch with the image of an armed Pepe the Frog is worn during a rally organized by the Virginia Citizens Defense League on Capitol Square near the state Capitol building in Richmond, Virginia, on Jan. 20, 2020. Chip Somodevilla / Getty Images file

The report comes as U.S. law enforcement officials and researchers at various levels have issued warnings about the growing threat posed by domestic extremists motivated by fringe ideologies and conspiracy theories. NCRI director Joel Finkelstein, a research scholar at the James Madison Program at Princeton University, said the report had been sent to members of Congress and the departments of Defense, Homeland Security and Justice, among others.

Paul Goldenberg, a member of the Homeland Security Advisory Council, said the report was "a wake-up call."

"When you have people talking about and planning sedition and violence against minorities, police and public officials, we need to take their words seriously," said Goldenberg, who is also CEO of the security consulting company Cardinal Point Strategies.

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Goldenberg said the report had "gone viral" within law enforcement and intelligence communities since its limited release last week. People are reading it and distributing it "far and wide," he said.

The current boogaloo movement was first noticed by extremism researchers in 2019, when fringe groups from gun rights and militia movements to white supremacists began referring to an impending civil war using the word "boogaloo," a joking reference to "Breakin' 2: Electric Boogaloo," a 1984 sequel movie about breakdancing.

The term is used to describe an uprising against a seemingly tyrannical or left-wing government, often in response to a perceived threat of widespread gun confiscation. For many, the word "boogaloo" — silly on its face — is used jokingly or ironically, but for others, the boogaloo memes are shared alongside violent text and images, seemingly to inflame an eventual confrontation.

In the last three months, boogaloo-related conversation has grown rapidly, according to the researchers, who found that use of the term has increased nearly 50 percent on platforms like Reddit and Twitter over the last few months. Increased exposure, the researchers warn, carries the danger of indoctrination.

Boogaloo extremists have used social media to "strategize, share instructions for explosives and 3-D printed firearms, distribute illegal firearm modifications, and siphon users into encrypted messaging boards en mass," according to the NCRI report. The report also notes how the boogaloo concept has been monetized, through merchandise advertised through Facebook and Instagram ads, and marketed to current and former members of the military.

On Facebook and Instagram, the researchers pointed to several boogaloo-themed public groups and accounts with tens of thousands of members and followers.

A spokesperson for Facebook said in an emailed statement that the company monitored groups that called for violence.

"We've been studying trends around this and related terms on Facebook and Instagram," the spokesperson said. "We don't allow speech used to incite hate or violence, and will remove any content that violates our policies. We'll continue to monitor this across our platform."

Since NCRI generated the report last week, membership in several boogaloo groups on Facebook has nearly doubled, according to an NBC News analysis. Two of Facebook's most popular boogaloo groups, which boasted nearly 20,000 followers during the same period, are no longer available this week.

Much like the OK hand symbol co-opted by white nationalists who later denied the association, the ambiguity of the term "boogaloo" works to cloak extremist organizing in the open.

"Like a virus hiding from the immune system, the use of comical-meme language permits the network to organize violence secretly behind a mirage of inside jokes and plausible deniability," the report states.

The term "boogaloo" has also been seen in real-world activism. At the Virginia Citizens Defense League's annual Lobby Day in Richmond in January, a group of protesters who go by the name Patriot Wave wore Pepe the Frog patches emblazoned with "Boogaloo Boys." One man carried a sign that read, "I have a dream of a Boogaloo." The rally was held on Martin Luther King Jr. Day.

NCRI was able to trace the origin of the use of the term "boogaloo" to 4chan's politics-focused message board, where racist and hateful memes often get their start. "Boogaloo" was often associated with apocalyptic and racist terms like "racewar" and "dotr," a white power fantasy that imagines a time when "race traitors" will be murdered.

The report tracked events when online chatter about an impending boogaloo spiked. The analysis found a peak during a November standoff in upstate New York between an Army veteran and police over a domestic dispute. The veteran, Alex Booth, chronicled the standoff on his pro-gun Instagram account, "Whiskey Warrior 556," claiming to followers that his guns were being confiscated. The incident made the boogaloo meme go viral and gained Booth over 100,000 followers.

The second boogaloo meme peak appeared around the House's impeachment of President Donald Trump, the report found.