During a Senate hearing in September, the FBI director described what the agency sees as the top four threats facing the United States.

FBI Director Christopher Wray told the Senate Committee on Homeland Security and Governmental Affairs that foreign terrorist organizations, homegrown violent extremists, cyberattacks, and malign foreign influence present the biggest threats to the United States.

In addition to the four threats the FBI has identified, the wider intelligence community and the Department of Defense have also highlighted that supply-chain vulnerabilities pose an additional threat to U.S. national security and private industry.

The threats come from both state and non-state actors, with China and Russia behind some of the challenges.

Homegrown Violent Extremists

Domestic terrorists are high on the FBI’s threat list.

The FBI categorizes Domestic Violent Extremists (DVEs) as individuals who commit violent criminal acts to further socio-political goals and who have been influenced by domestic factors, including racial, ethnic, anti-government, or anti-authority views.

On the other hand, individuals who believe themselves to be participating in a global jihad — or holy war — but aren’t members of a foreign terrorist organization, such as Al Qaeda or ISIS, fall under the Homegrown Violent Extremist (HVE) category.

According to the FBI, there are several similar characteristics between international and domestic terrorists. The most important of those is the danger that “lone wolves” and small cells of terrorists pose.

Because such individuals or cells are often radicalized online and take precautions to hide their activity and thinking, the FBI can’t act to stop them before they commit acts of terror. As a result, these terrorists are almost invisible to the intelligence community and law enforcement.

Further, small cells or “lone wolf” terrorists tend to go after soft targets, such as concerts, supermarkets, festivals, or places of worship, where dozens if not hundreds of people gather and can be targeted.

“Both of these threats, which together form the most significant terrorism danger to our country, are located primarily in the United States and typically radicalize and mobilize to violence on their own,” Wray said, adding that those actors’ ability to quickly mobilize without any indications, often due to their use of encrypted communications such as Signal and ProtonMail, “pose significant challenges to our ability to proactively identify and disrupt them.”

Foreign Terrorist Organizations

Twenty years after the September 11, 2001, terrorist attacks, terrorist groups still pose a threat to the United States.

According to the FBI, Al Qaeda and ISIS are actively planning attacks on the U.S. and against U.S. interests abroad, as well as against other Western countries.

The difference between the two terrorist groups has to do with their approaches. Al Qaeda seeks to conduct large-scale attacks that will kill lots of people and draw international attention. ISIS seeks to influence and motivate individuals and small cells of radicalized people to perform “lone wolf” attacks.

Iran, acting through its Islamic Revolution Guard Corps’ Quds Force, and its proxy forces are also actively plotting attacks against U.S. targets stateside and in the Middle East.

Cyber

Unsurprisingly, cyberattacks also pose a grave threat to U.S. national security and the U.S. economy.

Russia and China have been hacking their way to U.S. national, economic, and technological secrets for years now.

Despite the creation of a specific cyber center to coordinate and address these attacks, Moscow and Beijing keep at it, causing grave damage. The National Counterintelligence and Security Center has calculated that Beijing steals between $200 billion and $600 billion worth of economic secrets a year.

Theft at that scale can have profound impact — industrial espionage, for instance, has boosted China’s military modernization efforts.

Foreign Malign Influence

Malicious foreign influence is probably the least detectable of the major threats facing the United States.

The FBI and the rest of the intelligence community assess that foreign states are trying to influence U.S. national politics and public opinions, with the goal of sowing division.

In 2016, the Russian intelligence agencies sought to influence the U.S. presidential election, interfering “in sweeping and systematic fashion,” though they don’t appear to have altered votes and it’s not clear that they affected the election results.

Foreign influence operations include subversive, undeclared, coercive, and criminal activities to influence political sentiment and public discourse.

Although such influence operations aren’t anything new, the pervasiveness of social media and the ability of artificial intelligence to imitate human activity on social media has made them much harder to defend against.

According to the FBI, adversaries such as China and Russia are “hoping to reach a wide swath of Americans covertly from outside the United States” by fabricating fake identities on social media in order to “discredit U.S. individuals and institutions.”

Supply Chains

In addition to the four threats the FBI identified, vulnerabilities in the supply chain are also a source of major concern.

For example, if the USS Gerald R. Ford, the Navy’s new $13 billion aircraft carrier, requires a small auxiliary part that’s made overseas and a trade war or conflict breaks out, the U.S. wouldn’t be able to replace that part.

That’s a hypothetical scenario to highlight the importance of a robust supply chain, but those vulnerabilities have been put on display.

Early in the COVID-19 pandemic, demand for masks and other personal protective equipment skyrocketed, and most of the supply came from China. More recently, economies have been affected by ongoing delays and shortages of important industrial components, especially of semiconductors, most of which are made in East Asia. Deteriorating relations, or outright conflict, could create even worse problems.

Despite the many challenges on many fronts, Wray said the FBI continues to work with its partners to thwart plots and threats.

“No matter which threats have dominated the landscape over the last 20 years, the FBI has remained focused on prevention and disruption — sharing intelligence and making arrests before criminals and terrorists can act,” Wray said.

This article was written by Stavros Atlamazoglou and originally published on Insider.