The terrorist threat has changed dramatically in the 25 years since the September 11, 2001 attacks, evolving from highly organized transnational networks such as Al-Qaeda into a more fragmented landscape involving self-radicalized individuals, online propaganda, drones and increasingly sophisticated technology.
The contrast is illustrated by the case of Farhad N., who was only a few months old when Al-Qaeda operatives hijacked passenger planes and crashed two of them into the World Trade Center in New York, killing thousands.
Twenty-five years later, the Afghan-born man was sentenced to life in prison after driving a Mini Cooper into a crowd in Munich, killing two people and injuring dozens more.
Unlike the perpetrators of 9/11, Farhad N. was not identified as a member of a specific terrorist organization. Investigators said he appeared to have acted on his own after becoming radicalized online by extremist propaganda.
His case reflects a broader transformation in the nature of terrorism.
From organized networks to “lone wolves”
The attacks of September 11 were planned by Al-Qaeda, led by Osama bin Laden and sheltered by the Taliban government in Afghanistan.
The United States and its allies subsequently launched the “War on Terror,” overthrowing the Taliban government and conducting military and intelligence operations against Al-Qaeda and other militant organizations across Afghanistan, Iraq and elsewhere.
But the dismantling of terrorist safe havens did not eliminate the threat.
Instead, organizations adapted.
“Lone actors” or “lone wolves” increasingly became a central concern for security agencies. Individuals no longer necessarily need to join a terrorist organization to become radicalized or inspired to carry out an attack.
An American former diplomat with decades of counterterrorism experience told Radio Free Europe/Radio Liberty that this model is likely to become even more important.
“Nobody needs to be part of a group anymore,” the former diplomat said, arguing that individuals can be inspired by one or several organizations without being formally connected to them.
Retired U.S. General Joseph Votel, who played a major role in American counterterrorism operations after 9/11, said terrorist organizations have survived by continuously adapting.
“These terrorist organizations have survived. They have continued to adapt as much as they can… they have become more sophisticated,” Votel said.
The result, he argued, is a much more complicated security environment.
The internet has transformed radicalization
Social media and encrypted online platforms have fundamentally changed how extremist groups communicate and recruit.
Al-Qaeda and its affiliates have increasingly used online propaganda to reach audiences far beyond their traditional areas of operation.
Sara Harmouch, a terrorism expert and fellow at the Frontier Security Institute and George Washington University’s Program on Extremism, said Al-Qaeda in the Arabian Peninsula had significantly expanded its propaganda output following the U.S. withdrawal from Afghanistan.
She said AQAP has recently published statements and videos encouraging “lone wolves” in the West to carry out attacks in the United States and Europe.
The shift means that authorities are no longer dealing only with terrorist organizations that can be tracked through leadership structures, training camps and established communication networks.
They must also monitor an enormous online environment in which extremist ideas can spread rapidly and individuals can radicalize without direct contact with militants.
Al-Qaeda has also changed
The post-9/11 history of Al-Qaeda is not simply one of decline.
The organization developed affiliated branches in different parts of the world, including Al-Shabaab in Somalia and Jama’at Nusrat al-Islam wal-Muslimin, or JNIM, in the Sahel.
These groups combine local political and military objectives with Al-Qaeda’s broader ideological framework.
The decentralized structure has helped Al-Qaeda survive repeated attacks against its senior leadership and the loss of its safe havens in Afghanistan.
According to the article, recent UN assessments have continued to identify Al-Qaeda in the Arabian Peninsula as one of the organization’s most active branches.
The network has also maintained links between its regional affiliates, including cooperation involving financing and training.
This creates a security challenge that is fundamentally different from the centralized threat represented by Al-Qaeda in the years immediately before 9/11.
Technology is creating new vulnerabilities
The terrorist threat has also expanded into areas that barely existed as security concerns 25 years ago.
Drones, artificial intelligence and social media have created new opportunities for extremists to spread propaganda, conduct surveillance and potentially facilitate attacks.
AI could further lower the barriers to radicalization by allowing extremist actors to produce propaganda and communicate with potential recruits at greater speed and scale.
At the same time, security agencies face the challenge of distinguishing genuine threats from the enormous volume of online activity generated every day.
The technological transformation therefore cuts both ways: the same tools that can assist law enforcement can also make terrorist communication and recruitment more difficult to detect.
Iran and Al-Qaeda: A pragmatic relationship
Another complication is the relationship between Iran and Sunni extremist organizations such as Al-Qaeda.
Although Iran is a Shiite state and Al-Qaeda is a Sunni jihadist organization, their interests have at times overlapped.
UN reports have said that senior Al-Qaeda figure Saif al-Adel has lived in Iran, while analysts argue that Tehran has viewed the organization as potentially useful because its activities can impose costs on the United States.
Iran has also maintained longstanding support for Hezbollah and Hamas, both of which Washington has designated as terrorist organizations.
Beyond the Middle East, Tehran has also been accused of using criminal intermediaries to conduct attacks, potentially allowing the Iranian government to maintain plausible deniability.
A 2025 report by the Combating Terrorism Center at West Point highlighted what it described as Iran’s increasing use of criminal networks as intermediaries for attacks outside the region.
Is the West losing its counterterrorism capacity?
As terrorist threats have evolved, experts interviewed by RFE/RL also warned that Western governments may be reducing some of the capabilities developed during the post-9/11 period.
The United States has shifted its strategic focus in recent years toward great-power competition, particularly involving Russia and China, while conflicts in Ukraine and the Middle East have absorbed significant political and military attention.
Tom Sanderson of the Center for Strategic and International Studies warned of declining attention, budgets and personnel devoted to counterterrorism.
Bruce Hoffman of the Council on Foreign Relations similarly described a major loss of personnel within the U.S. State Department’s counterterrorism structure.
The concern is not necessarily that terrorism has become more powerful than it was in 2001.
Rather, the threat has become harder to define.
Jonathan Schroden of CNA said U.S. policy has increasingly shifted from trying to completely defeat terrorist organizations toward managing the threat they pose and keeping it away from American territory.
That approach may have been effective in reducing the likelihood of another large-scale attack comparable to 9/11. But it also reflects an uncomfortable reality: terrorism has not disappeared.
It has fragmented, decentralized and adapted.
A different terrorist threat 25 years later
The central lesson of the past quarter-century is that defeating one terrorist organization does not eliminate the underlying threat.
Al-Qaeda survived the destruction of its original safe havens. Its affiliates expanded across Africa and the Middle East. The Islamic State introduced another model of territorial control and online mobilization. And increasingly, individuals inspired by extremist propaganda can act without formal organizational ties.
The next phase could be even more decentralized, with artificial intelligence, drones and social media giving individuals capabilities that previously required access to sophisticated terrorist networks.
Twenty-five years after 9/11, the question for security agencies is therefore no longer simply where the next terrorist organization is operating.
It is increasingly how an individual can become a terrorist without ever joining one.
