Twenty-five years after the September 11, 2001 attacks, the United States has constructed a formidable national security apparatus designed to prevent another assault on the scale of that day. However, the nature of terrorist threats has evolved, shifting from organized, externally directed plots to decentralized, often self-radicalized individuals inspired by online propaganda.
Javed Ali, a former counterterrorism official who served at the Department of Homeland Security (DHS) and the FBI, stated that while America is safer from a 9/11-style attack, today's threats are more difficult to detect. The U.S. has not experienced another terrorist attack remotely approaching the scale of 9/11, which killed 2,977 people. This success is attributed to dismantled al-Qaeda networks, new agencies, enhanced surveillance, watchlists, and improved intelligence sharing systems. The 2026 U.S. intelligence community assessment noted that counterterrorism operations have degraded al-Qaeda and ISIS's ability to plan large-scale attacks against the U.S. homeland.
Building a Security State
The response to 9/11 led to the creation of the Transportation Security Administration (TSA) just over two months after the attacks, federalizing airport security. In 2003, the Department of Homeland Security was established, consolidating 22 federal agencies and offices. Today, DHS employs over 260,000 people across a wide range of security and emergency response missions. The 9/11 Commission identified a pre-attack breakdown in intelligence sharing and accountability, prompting efforts over two decades to close these gaps. The Costs of War project estimates that post-9/11 wars and homeland security efforts have cost approximately $8 trillion and over $1.1 trillion, respectively.
The Evolving Threat Landscape
Even after dismantling core al-Qaeda operations, the threat persisted and evolved. During Ali's tenure at DHS, officials addressed plots involving al-Qaeda and its affiliates, such as a 2006 plot to bomb transatlantic airliners. The rise of ISIS, which emerged from al-Qaeda in Iraq, presented a new challenge. U.S. counterterrorism efforts increasingly focused on identifying individuals radicalizing within Western countries rather than trained operatives sent from abroad. This shifted further to attacks by lone actors with no direct operational ties to overseas organizations.
The Digital Age of Terrorism
Current government threat assessments reflect this transformation. The 2026 Annual Threat Assessment from the Office of the Director of National Intelligence indicates that Islamist terrorist groups, facing setbacks in conducting large-scale attacks, are focusing on information operations and propaganda to inspire individuals. In 2025, there were at least three Islamist terrorist attacks in the U.S., and law enforcement disrupted 15 U.S.-based plotters, many with online contact with terrorist entities. An example cited was the January 1, 2025, New Orleans truck attack, where the perpetrator had become increasingly isolated and adopted extremist views online. The FBI identifies lone actors and small cells radicalized online as the primary terrorism threat due to their difficulty in detection.
In contrast to the 9/11 plot, which involved 19 hijackers, overseas leadership, financing, and extensive planning, lone actor attacks often present fewer discernible pieces of information for investigators to collect. Many recent attackers have not previously come to the attention of law enforcement, making preemptive intervention extremely challenging.
A Security System for Yesterday?
Some critics argue that the institutions created after 9/11 have become too large and focused on past threats. Morgan Murphy, who served in the Trump administration, contends that excessive bureaucracy was built around the 9/11 threat while other vulnerabilities, such as supply chain infiltration and cyber threats, grew. Theo Wold, also from the Trump administration, criticized the reliance on large bureaucracies and expansive government authorities, suggesting a more narrowly targeted national security model is needed.
The current threat landscape extends beyond traditional terrorism. Intelligence assessments warn of espionage and potential disruption efforts by China, Russia, Iran, North Korea, and ransomware groups targeting U.S. networks and critical infrastructure. The acceleration of cyber capabilities through artificial intelligence and state adversaries developing advanced missile systems further expand the security challenge. Ali emphasizes the need to confront emerging terrorist threats before they gain operational capability, cautioning against complacency. While the U.S. has become far safer from large-scale attacks like 9/11, the nation faces the more complex challenge of recognizing and preventing attacks that do not resemble those of the past.