How to hunt a lone wolf: Countering terrorists who act on their own

French police secure the area as the investigation continues at the scene near the heavy truck that ran into a crowd at high speed killing scores who were celebrating the Bastille Day July 14 national holiday on the Promenade des Anglais in Nice, France, July 15, 2016. REUTERS/Eric Gaillard - RTSI28V
Editor's note:

In the last two years, “lone wolf” jihadists seemed to emerge as the new face of terrorism, writes Daniel Byman. Although lone-wolf attacks are hard to prevent, governments in the West can do several things to make them less likely and to prepare for those that do occur. This piece originally appeared on Foreign Affairs.

In the last two years, “lone wolf” jihadists seemed to emerge as the new face of terrorism. In December 2015, husband and wife Syed Rizwan Farook and Tashfeen Malik attacked a Christmas party held by Farook’s employer, the San Bernardino County Department of Public Health, killing 14. In June 2016, Omar Mateen killed 49 people at a gay nightclub in Orlando, Florida—the deadliest attack on U.S. soil since 9/11. And in July, Mohamed Lahouaiej Bouhlel drove a truck through a Bastille Day celebration in Nice, killing 86 people.  The attacks by the San Bernardino killers, Mateen, and Bouhlel followed an increasingly common pattern: the Islamic State (also known as ISIS) claimed credit for them, but the perpetrators appear to have planned and executed their operations alone.

Analysts traditionally define a lone wolf as a terrorist who is not part of a group or directed by an outside organization. In reality, few lone wolves truly act alone: Farook and Malik were a married couple, and some security officials believe that Bouhlel had been in contact with suspected extremists in his neighborhood. Nevertheless, the label is important: terrorists who act without external guidance pose a different threat, and call for a different policy response, than do those who are directed by an extremist group.

Lone wolves are an old problem, but in recent decades, the number of attacks by them has grown. And it won’t fall anytime soon: ISIS has embraced the tactic, and recent successes may well inspire copycats. And although lone wolves usually kill few people, they have an outsize political impact. In both the United States and Europe, they are fueling Islamophobia, isolating Muslim communities, and empowering populist demagogues.

Although lone-wolf attacks are hard to prevent, governments in the West can do several things to make them less likely and to prepare for those that do occur. First, they should work to keep lone wolves isolated. Terrorists are far more likely to succeed if they can coordinate with others, especially if they have the help of an organized group, such as ISIS. Second, governments should build strong relationships between Muslim communities and law enforcement agencies. The friends, family, and neighbors of would-be terrorists are more likely than the security services to know if something is amiss, so governments must gain their trust. This will mean giving security officials the flexibility to intervene in ways that do not involve jail sentences, such as by allowing them to supervise individuals without arresting them. Third, governments should direct security services to monitor and infiltrate jihadist social media accounts, and encourage private companies to shut them down, to identify individual terrorists and disrupt their communications. Finally, and most important, governments should try to discredit the ideology embraced by lone wolves. Yet doing all these things would only reduce the lone-wolf threat, not end it. It is impossible to stop every violent individual from picking up a gun and shooting.

It is impossible to stop every violent individual from picking up a gun and shooting.


Today, the lone wolves who get the most attention are Islamist extremists, but since the threat began, such attackers have emerged from fanatical movements of all stripes. In 1995, the white supremacist Timothy McVeigh launched the deadliest terrorist attack on U.S. soil before 9/11 when he bombed the Alfred P. Murrah Federal Building in Oklahoma City, killing 168 and wounding hundreds more. In 2010, James Lee, who mixed environmental activism with anti-immigrant sentiment, took three people hostage in Maryland. Dylann Roof, a white supremacist, murdered nine African American parishioners at a historically black church in Charleston, South Carolina, in 2015.

Groups usually encourage lone wolves when they are too weak to carry out organized attacks themselves. In 1983, the American white supremacist Louis Beam called for “leaderless resistance” to the federal government. Traditional groups with tight command and control “are easy prey for government infiltration, entrapment, and destruction,” Beam wrote, so small groups and individuals should work independently. Over a decade ago, the jihadist fighter and theorist Abu Musab al-Suri encouraged lone-wolf attacks for the same reason. He pointed out that jihadists had lost hundreds of fighters when they confronted U.S. forces in large groups during the post-9/11 wars in Afghanistan and Iraq. The solution, Suri argued, was to rely on “single operations . . . carried out by individuals or small groups.”

Beam and Suri’s logic is catching on. In 2012, the sociologist Ramon Spaaij found that from 1970 to 2010, the number of lone-wolf attacks per decade grew by 45 percent in the United States and by over 400 percent across 14 other developed countries, although the absolute numbers remained low. And since ISIS gained strength in 2014, the West has seen another increase. In July 2015, Mohammad Youssef Abdulazeez killed five people at a military recruitment center and a U.S. Navy Reserve base in Tennessee. In September 2016, lone wolves executed two separate plots. Ahmad Khan Rahami allegedly planted two bombs in New York City and one in New Jersey—one went off in Manhattan but did not kill anyone. On the same day in Minnesota, Dahir Adan stabbed and injured ten people at a mall. And in November, Abdul Razak Ali Artan, a legal permanent resident of the United States who was a refugee from Somalia, rammed his car into a group of his fellow students and faculty and staff members at Ohio State University and stabbed several more before a security guard shot him dead. Europe has seen even more attacks, with strikes in Tours, Lyon, and Copenhagen. Both the United States and Europe saw roughly twice as many successful lone-wolf attacks in 2015 and 2016 as they did from 2011 to 2014.

Although the overall trend is clear, experts struggle to identify precise numbers, as the boundary between lone wolves and coordinated attackers is unclear. When it comes to affiliation with a group, terrorists exist on a spectrum. At one end lie established organizations. The 2015 Paris attacks, for example, in which terrorists killed 130 people, involved a relatively large network of individuals operating in Belgium and France. ISIS fighters had trained many of them in Syria, and the group’s leadership coordinated the operation. At the other end of the spectrum lies someone such as Ted Kaczynski, the so-called Unabomber, who killed three people and injured more than 20 others during a 17-year campaign of mail bombings. Kaczynski lived alone, had no ties to any organized group, and formulated his own agenda.

Individuals such as the San Bernardino killers or Mateen lie closer on the spectrum to the Unabomber than to the Paris attackers, but they were not totally isolated. Although such attackers act alone, they all still feel some connection to a broader cause. The lectures of the U.S.-born al Qaeda ideologue Anwar al-Awlaki inspired the San Bernardino killers, for example, and although they had no direct contact with ISIS, during the attack they pledged loyalty to the group’s leader (whose name they had looked up on the Internet only that day). Closer to the organized end of the spectrum was Nidal Hasan, who in 2009 killed 13 people in a shooting rampage at Fort Hood, in Texas. Hasan drew inspiration from Awlaki’s teachings but also exchanged e-mails with the preacher, in which the two discussed jihad (although they did not plan any particular attack).


The increase in lone-wolf attacks has been driven in part by ISIS’ embrace of the tactic. For most of its history, ISIS focused on Iraq and Syria. It did call for attacks in the West in 2014, but most of its propaganda urged supporters to immigrate to the areas under the group’s control, where they could defend and expand the state and live life as virtuous Muslims under ISIS’ just rule. In early 2016, however, an ISIS spokesman declared that “the smallest action you do in the heart of [the West] is dearer to us than the largest action by us and more effective and more damaging.” ISIS made this shift because attacks by the U.S.-led coalition have shrunk its territory in Iraq and Syria and eroded its ability to carry out large-scale operations. The group is short of funds and having a tougher time recruiting foreigners. Like all terrorist groups, ISIS needs victories to inspire new recruits and maintain morale among the existing cadre. Lone-wolf attacks can provide at least a few victories.

New technologies have also contributed to the lone-wolf phenomenon. Back when Beam and other white supremacists were urging individuals to carry out attacks, they were trying to promote their ideas and give their effort overall coherence by disseminating a few printed tracts. The Internet, particularly since the rise of social media, has put that process on steroids. Now even small groups can spread their ideas far and wide. Young Muslims all over the West need only search Google to read or listen to the words of ideologues such as Awlaki.

Groups usually encourage lone wolves when they are too weak to carry out organized attacks themselves.

Perhaps most worrisome, lone-wolf attacks seem to be entering the broader cultural imagination in the West, providing a template to violence-prone misfits who might otherwise not have acted on their murderous impulses. Put another way: people who might not have the means, opportunity, or even desire to actually join a terrorist organization might nevertheless come to see lone-wolf attacks as an appealing way to express their rage. Consider that many recent lone-wolf attackers were not longtime adherents to radical ideas. Rather, they seem to have been people who were searching for meaning in their lives and who found it by committing spectacular violence in the name of a movement—without having invested the time and energy it would have taken to actually join the movement in a more committed way or having borne the associated risk.


As Beam, Suri, and other proponents of lone-wolf attacks have argued, governments find it fiendishly difficult to stop them. To break up most terrorist plots, officials monitor communications to identify and locate the associates of known suspects. Lone wolves, however, have few previous connections to known terrorists and rarely communicate with them.

Lone wolves are also cheap. They are usually untrained, and they finance themselves, so a group can take the credit for free. The wider a group spreads its ideology, the larger the supply of cheap attacks. Lone wolves also allow a terrorist group to claim responsibility for violence that the larger public would otherwise have ignored. In Lyon in 2015, Yassin Salhi, a delivery driver, beheaded his boss before trying to blow up gas canisters at a processing plant. Farook, one of the San Bernadino attackers, worked at the county health department whose Christmas party he and his wife targeted. In both cases, had the attackers not pledged loyalty to ISIS, law enforcement and the media might have described the attacks as workplace violence, not terrorism. Once officials attributed the acts to ISIS-linked terrorists, media attention—and thus the psychological impact—went through the roof.

Finally, lone wolves frighten people because they can strike anywhere. The 9/11 attacks targeted the symbols of U.S. financial, military, and political power; for many, the attacks struck at their identity as Americans but did not affect their personal security. A massacre at a nightclub or an office party, by contrast, hits much closer to home.

Despite these advantages, most terrorist organizations have shied away from lone wolves. Groups avoid them partly because they often fail. The high death tolls of the attacks by Mateen and Bouhlel were unusual. Most lone wolves kill only a few people, if any, before police neutralize them. The Tsarnaev brothers, who in 2013 killed three people with primitive bombs at the Boston Marathon, were typical.

Lone-wolf attacks mostly flop because the perpetrators are untrained in violence. The terrorism scholar Thomas Hegghammer has found that the involvement of someone with prior combat or terrorist experience both dramatically improves the odds of a plot’s succeeding and makes the attack deadlier. By using untrained militants, groups risk damaging their reputations with repeated failures.

Lone-wolf attacks seem to be entering the broader cultural imagination in the West.

Another problem is that group leaders do not control lone wolves, who might adopt tactics that hurt the broader cause. Violence without a strategy terrifies, but it can also backfire. McVeigh’s attack, for example, discredited other far-right movements: McVeigh claimed he was dealing a blow to a tyrannical government, but the death of 19 children and three pregnant women in the bombing made it hard for other antigovernment zealots to defend him. The fact that many lone wolves suffer from mental illness makes this lack of discipline even more likely. Unfortunately, ISIS seems to be ignoring these constraints. It has so far accepted, and actually encouraged, lone-wolf violence committed in its name—a surprising turn even considering the low standards of terrorist groups.


Lone-wolf attacks are having a far more powerful impact than their relatively modest death tolls might suggest. In the United States and Europe, they are encouraging Islamophobia, shattering good relations between Muslims and non-Muslims, and even threatening liberal democracy itself.

A report published last year by the Bridge Initiative at Georgetown University found that “Islamophobic political vitriol intensified” in the period following the San Bernardino attack. After the Orlando shooting, a Gallup poll found that almost 40 percent of Americans favored then Republican presidential candidate Donald Trump’s proposal to ban Muslims from entering the United States. And the effects weren’t just rhetorical: according to the FBI, anti-Muslim hate crimes in the United States rose by 67 percent from 2014 to 2015. In Europe, refugees have faced a similar backlash. A recent Pew poll indicated that 59 percent of Europeans feared that the presence of refugees would increase the likelihood of terrorist attacks in the EU. In the first four months of 2016, arsonists carried out 45 attacks on refugee camps in Germany. And in northern Italy, far-right protesters have repeatedly torched prayer rooms in refugee camps.

Such Islamophobia can begin a vicious cycle. When public opinion turns on Muslim communities, they tend to withdraw into themselves, trust law enforcement—and the wider society—less, and risk turning into breeding grounds for radicals. For instance, for four months following the Paris attacks, a network of friends, family, and petty criminals helped Salah Abdeslam, one of the perpetrators, evade a massive international manhunt while hiding in his hometown of Molenbeek, in Belgium. Groups such as ISIS often highlight discrimination and hostile rhetoric and use decisions such as the French government’s ban on wearing the Islamic veil in public places as proof that the West is at war with Islam.

Meanwhile, demagogues have exploited the fear of Muslims in order to undermine public confidence in government, call for draconian security measures, reject refugees fleeing violence, and turn societies against religious minorities, particularly Muslims. Far-right movements are growing stronger in several European countries. Hungary’s prime minister, Viktor Orban, has long played on public fear of Muslim foreigners to win support for turning his country into what he has termed an “illiberal state,” arguing that the community, not the individual, should lie at the center of politics. To that end, he has centralized power, restricted media freedom, and undermined the independence of the judiciary. In December 2016, Austria came close to electing Norbert Hofer of the far-right Freedom Party to the presidency, and anti-immigrant far-right parties have emerged from the political fringes in France and the United Kingdom. In the latter, anti-immigrant sentiment played a major role in the decision to leave the European Union. In the United States, Islamophobia and fear of terrorism—despite few attacks or fatalities on U.S. soil since 9/11—fueled the rise of Trump and other anti-immigrant politicians. Trump’s calls for establishing a Muslim registry, renewing the use of torture, and monitoring mosques as a matter of course all contradict the U.S. principles of freedom of religion and respect for human rights.


Governments can reduce the number of lone-wolf attacks, even though official efforts cannot stop them completely. One of the best ways to do so is to keep lone wolves lonely: the less they interact with potential coconspirators, and especially with groups that can give them direction and training, the less dangerous they will be. Officials must therefore focus on gathering intelligence, arresting suspected cell leaders, and destroying terrorist command centers with drone strikes. If leaders cannot reach out to potential followers, they cannot train terrorists or organize them into groups large enough to conduct major attacks. Better lone wolves than wolf packs.

It is also important to try to make lone-wolf attacks less lethal. The United States has programs that limit the possession of explosives to only those with a legitimate need, making it far harder for terrorists to build bombs. Taking a similar approach to semiautomatic weapons would be sensible. Unfortunately, gun control—even in the context of counterterrorism—seems to be a political nonstarter.

Intelligences services should also work to identify lone wolves ahead of time. On this front, ISIS’ heavy reliance on social media makes the group vulnerable. Monitoring social media can help officials spot potential attackers without previous connections to other terrorists, as online operatives may encourage them or they may post their intentions online. One of the two Islamist terrorists who last July killed a priest in a church in northern France, for example, reportedly announced his intention to do so well in advance on social media.

To hinder ISIS’ recruitment, the U.S. government should continue to press companies such as Facebook and Twitter to tighten restrictions on accounts linked to the group, monitoring users more regularly and suspending their accounts when necessary. In 2015 and 2016, as ISIS’ reliance on social media became a public concern, several companies, including Twitter, suspended accounts linked to ISIS. Companies bristle when they perceive government censorship, but in reality, the government is simply asking them to abide by their own terms of service, which often place tight restrictions on potentially illegal activity.

ISIS will adapt to suspensions by creating new accounts and taking to new forms of communication, but the new means of communication will often fall short of the old ones. Although ISIS had tens of thousands of accounts on Twitter, for example, it used only a small fraction of them to spread most of its propaganda. Suspending these accounts can set back recruitment. A recent study by the terrorist social media analysts J. M. Berger and Heather Perez found that ISIS’ Twitter presence declined from 2014 to 2016 in part because of Twitter’s efforts to shut down its accounts.

Governments can also plant disinformation in ISIS’ network. The group is already highly suspicious of infiltrators—it has rejected or even executed foreign fighters on suspicion of spying—so officials should exploit this paranoia by playing up the presence of moles and the likelihood of defections. Law enforcement should also carry out offensive cyberattacks on extremist sites. These attacks could alter the sites so that they pass on false contact information, present distorted propaganda, or otherwise sow confusion, or they could simply take the sites down.

Countering ISIS’ broader message is also important, albeit exceptionally difficult. In theory, doing so could hurt the group’s fundraising and recruitment. In practice, however, government efforts are often cumbersome, cautious, and ineffective. The best voices are those of former recruits or others with firsthand experience with the group, not those of officials. The former can talk credibly about the dismal conditions in areas controlled by ISIS, the killing of jihadists, and other problems that run counter to the group’s propaganda.

One imperative—and the one governments are least likely to heed in the aftermath of an attack—is to build support within Muslim communities for official counterterrorism efforts. If a community has good relations with the police and the rest of society, it will have fewer grievances for terrorists to exploit and its members will have stronger incentives to point out malefactors in their midst. In the United States, law enforcement could achieve better results by increasing their engagement with Muslim communities. In particular, officials should base their relationships with Muslim communities on more than just fighting terrorism. They should address crime and anti-Muslim harassment and help immigrants access social services. In addition, they should work with community leaders in advance on plans to protect their communities from the Islamophobic violence that often follows jihadist terrorist attacks. Situating terrorism in a broader context of public safety is more effective than isolating it, as Muslim communities rightly fear that law enforcement will focus only on terrorism while ignoring anti-Muslim crimes.

In addition, U.S. law enforcement must recognize the remarkable diversity of American Muslims, among whom ethnicity, sect, and tradition all vary widely. Different communities may have different concerns, different leaders, and different news sources. Local governments should take care to hire diverse police forces and train their members in cultural awareness.

A culture of greater resilience would also help. Despite the relatively low number of terrorism-related deaths on U.S. soil since 9/11, public fear of terrorism remains high. During his presidency, Barack Obama tried to highlight the United States’ many counterterrorist successes. Trump and other politicians should do the same and make Americans aware of the low risk, rather than attempting to exploit people’s fears for political gain.

These measures, alone or in combination, would not stop all lone wolves. But they would allow law enforcement to catch more of them and reduce the lethality of those attacks that go undetected. Most of all, they would diminish the political impact of lone-wolf attacks—and thus make the phenomenon as a whole less dangerous.