Fear and concern over ISIS-inspired terrorist attacks on U.S. soil has been turned up a notch in the last few months, thanks to ISIS’s thriving social-media campaign. A State Department report released Friday officially lists the self-proclaimed Islamic State as the world’s leading terror organization, citing not only the rapid advance and particular brutality of the group but also its “adroit” use of social media and ability to inspire “lone wolf” attacks.

“These attacks may presage a new era in which centralized leadership of a terrorist organization matters less, group identity is more fluid, and violent extremist narratives focus on a wider range of alleged grievances and enemies with which lone actors may identify and seek to carry out self-directed attacks,” according to the report.

Case in point: the shootings in Garland, Texas, and their aftermath.

In the past five weeks, nine young men in Garland, Boston, and most recently New York and New Jersey, have either been arrested for allegedly attempting to carry out ISIS-inspired attacks, or killed by law enforcement in a confrontation.

The attack in Garland, where two men opened fire outside a Draw Muhammad contest, was the first ISIS-inspired attack launched on U.S. soil. The shooters, Elton Simpson and Nadir Soofi, only managed to superficially injure a security guard before they were killed.

The reactions on social media to the Garland attack and to the arrests of individuals in other cities offers a microcosm into how ISIS’s social-media campaign is operating on a grassroots level, and how law enforcement is trying to nip the epidemic in the bud.

Though Simpson tweeted at an ISIS fighter before the attack, other than loose connections on social media and alleged confessions made to law enforcement in which they revealed their intended allegiance to ISIS, none of the individuals appear to have any formal ties to the terror group. No one other than the alleged perpetrators has been killed or seriously injured. Even so, the recent activity has served to fuel ISIS’s social media campaign.

“It was the lack of success that inspired people,” said Karen Greenberg, the director of the Center on National Security at Fordham University, explaining why the shooting riled up so many ISIS wannabes. Simpson and Soofi’s death may have motivated the young men in Boston and New York to finish the job, or at least try to, she suggests.

The FBI was immediately concerned about the fallout after Garland.

“I know there are other Elton Simpsons out there,” FBI Director James Comey told reporters just a few days after the shooting.

While ISIS has been a threat to American interests overseas since its emergence in 2013, at first the main fear was the possibility that U.S. citizens may leave and join the terror group.

Then last fall, ISIS began to amp up the call for followers to attack the U.S. and France in response to drone attacks. A few months later, Said and Chérif Kouachi killed 11 people in an attack on the offices of Charlie Hedbo in Paris, quickly followed by a man named Amedy Coulibaly, who killed four people in a kosher supermarket. The publication frequently depicted satirical cartoons of the Prophet Muhammad, and Coulibaly claimed to have carried out the attack in the name of ISIS.

In his interview with reporters after the Garland attack, Comey blamed social media for egging on “disturbed people.”

“It’s like the devil sitting on their shoulders, saying ‘Kill, kill, kill,’'” he said.

Following the Garland attack, ISIS writers in their sleek magazine Dabiq not only stated that first lady Michelle Obama would sell for about $40 on their slave market—creating a viral reaction in Western media markets—but they hailed Soofi and Simpson as “lions.”

The two men “took it upon themselves to remind the enemies of Allah and His Messenger (sallallāhu ‘alayhi wa sallam) that as long as they choose to wage war on Islam, they would have no peace.”

“Their determination to support the cause of Allah and punish those who insult the Prophet (sallallāhu ‘alayhi wa sallam) should serve as inspiration to those residing in the lands of the crusaders who are still hesitant to perform their duty.”

Much of ISIS’s ideology is disseminated through social media. According to a Brookings report, The ISIS Twitter Census: Defining and Describing the Population of ISIS supporters on Twitter, by J.M. Berger and Jonathan Morgan, there were at least 46,000 users in October-November 2014, with one in five speaking English. Many of ISIS’s followers tweet at rapid rates.

Though many of those accounts are frequently suspended, the online community survives because of the “whack-a-mole” effect. When one account dies, other supporters direct followers to the new accounts of previously suspended users.

But it’s not just the flashy and extensive ISIS propaganda machine that attracts followers. Berger says most of ISIS’s success is due to the high level of personal engagement. “Circles of users will surround a potential recruit and get involved not just directly but with the recruit’s other social networks, for instance trying to insulate them against unwanted attention by outsiders,” he explained in an email.

Recruiters include both fighters and supporters overseas, he says, “They’re patient, and will interact with a potential recruit over a long period of time if necessary, sometimes steering them in the direction of a particular kind of action.”

In New York, 20-year-old Munther Omar Saleh, an American aeronautics student in Queens—now facing charges for conspiring to support the terror group after his arrest last weekend—was allegedly operating one of about 400 American pro-ISIS Twitter handles. According to the complaint, after the attacks in Garland he was watching Twitter to see how members of ISIS reacted to the Garland shooting online.

Allegedly, he was not only soaking in ISIS’s message about the attack, but perpetrating their message, too.

He allegedly retweeted a post about Soofi and Simpson becoming martyrs. Then he retweeted an image with ISIS’s official statement, using an alternate acronym for the group: “IS claim responsibility for Texas attack and tell America that what’s coming will be even worse.”

Saleh had been tweeting about ISIS on his public Twitter account for a while, according to the criminal complaint against him. “I fear AQ could be getting too moderate,” he wrote in September 2014.

Federal agents were taking notice.

Though prosecutors have not released all of the information about his case, in the complaint Saleh’s social-media presence was used as evidence that he intended to carry out an attack in behalf of ISIS. The FBI cites his tweets as evidence that he was translating material for ISIS, too.

“Subhan Allah, IS is known for their high end videos, great weaponry, and quality fighters,” he wrote last February after joining aerodynamics school a month prior. (“Subhan Allah” means “glorious is God,” according to the complaint.)

After the attack in Garland, ISIS called for attacks on U.S. military bases. The security alert was raised was to “Bravo.” ISIS, meanwhile, was also asking for the “slaughter” of Pamela Geller, the anti-Muslim activist who held the contest in Garland.

Within hours of ISIS’s social-media blasts, Saleh appeared to be getting more serious about carrying out an attack, according to the complaint. He began looking at websites for the U.S. Army Rangers, U.S. special forces, as well as running searches for “training and equipment” and “gear and weapons.”

Law enforcement officials had observed him before on two occasions. A police officer said he was acting peculiarly near the George Washington Bridge in March. Federal agents questioned him, monitored his communications, and had informants communicate with him online.

On May 7, days after the attack, Saleh allegedly emailed himself information on how to make a bomb and told a federal informant online, “I’m in NY and trying to do an Op.”

“I’m very sorry, but I was ordered by [ISIS] officials not to talk to anyone,” he added.

His online searches were for watches, pressure cookers, and a lava lamp—all potential tools to build a bomb, says the FBI. Saleh’s relationship with the bureau came to a head last weekend. Saleh, aware that agents were following him, became upset. He started to drive erratically and then ran at the agents’ car. He had a knife in his waistband and was arrested soon after.

Saleh’s associate Fareed Mumuni, 21, was arrested Wednesday and charged with attempted murder and conspiracy to assist a terrorist group after he tried to stab an FBI agent with a kitchen knife. The agent was searching Mumuni’s home in the wake of Saleh’s arrest. The stab wounds did not penetrate his body armor, according to NBC News.

Saleh had been instructing Mumuni on how to carry out an attack, according to the complaint. The plan sounded more or less like a scene from Grand Theft Auto. He wanted Mumuni to set off a bomb, then run over law-enforcement officials in a vehicle and steal their guns.

Samuel Rahamin Topaz, 21, arrested on Thursday for material support of terrorism, was arrested as part of the same conspiracy, according to NBC News. The complaint against Topaz does not detail who his alleged co-conspirators are.

Earlier, in Boston, three young men fueled by the events in Garland also allegedly plotted a violent attack. Usaama Rahim, 26, David Wright, 25, and Nicholas Rovinski, 24, allegedly spoke of beheading Geller. But then, allegedly, at the last minute Rahim changed course and decided to go after police officers or the “boys in blue,” as he called them in a phone call recorded shortly before his death.

Rahim was shot to death by a Boston police officer and an FBI agent after members of a Joint Terrorism Task Force approached him in a parking lot on June 2. Rahim allegedly lunged at the officers with a 15-inch knife.

On Friday, Wright and Rovinski pleaded not guilty to all charges.

The JTTF had been following Rahim 24/7 for a week, since the day he ordered the knife on Amazon. The day before he made the purchase, ISIS fighter and recruiter Abu Sa’eed al-Britani called on social media for followers to “Go stab an officer & go prison where u can worship Allah without distraction,” according to the International Business Times.

“I think that we’re going to see more on this, unfortunately,” says Massachusetts Democratic Congressman William Keating, who sits on the Homeland Security committee. After the Boston and Garland attacks, Congress held a hearing dubbed “Terrorism Gone Viral.”

“This is a threat that is very real and it’s very difficult on many fronts, and it is hard to trace,” he says.

Don Borrelli—a former FBI agent and assistant special agent in charge at the New York JTTF, who left his post after 25 years to work at the Soufan Group—says that when he was working terrorism cases, al Qaeda propaganda was “so horribly boring to an average teenager it was worse than listening to a high-school science teacher.”

ISIS is much more appealing to young people. The problem for law enforcement is determining who is actually going to carry out an attack. “You have people that are curious, you have people who are trying to stick one toe in the water but they haven’t committed, you have the people that are hell bent,” he explains.

Distinguishing between an actual attack and online tough talk may prove difficult in the cases in Boston and New York, where the accused only allegedly became violent after they were approached by law enforcement.

Mike German, another former FBI agent who now works for the Brennan Center for Justice, says he’s still waiting for more information to come out about the incidents in Garland, New York, and Boston. But without formal connections to ISIS, he wonders if the response to social-media calls about terrorism may be overblown in some cases, and charging people for assisting terror groups based on their social-media associations may actually inspire more attacks.

“When stories about these acts that are supposedly inspired by these outside groups get publicized, the sensationalization creates an incentive for some other troubled person to make themselves famous for doing some inappropriate thing.”