MI5 Chief Warns Next 9/11-Style Attack Could Emerge From Unexpected Threat

Britain’s domestic intelligence chief has warned that the next major security shock could emerge from an unexpected direction if intelligence agencies become too focused on threats from the past. MI5 Director General Ken McCallum issued the warning as the UK marked 25 years since the September 11, 2001, attacks in the United States.

In an opinion piece published on Friday, McCallum said intelligence agencies must learn from previous attacks without allowing past events to determine how they prepare for future threats. He stressed that the next major attack would, by its nature, be different from the previous one.

McCallum warned that security agencies could make the mistake of becoming highly effective at confronting yesterday’s adversaries, tactics and targets while failing to identify an emerging threat elsewhere. He said the next strategic shock could already be developing in an area that authorities are not currently monitoring closely enough.

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The MI5 chief also highlighted the continued threat posed by al-Qaida and other militant organisations seeking to carry out attacks capable of causing mass casualties. Although al-Qaida has been significantly weakened, its ambitions and those of other extremist groups remain a concern, he said.

McCallum pointed to a recently disrupted Islamist plot in northern England as an example of the continuing danger. According to him, the alleged plan involved gun attacks targeting the Jewish community in Manchester and could have resulted in hundreds of deaths.

At the same time, Britain’s security challenges are no longer limited to terrorism. McCallum said MI5 is increasingly dealing with state-backed hostile activity, including sabotage conducted through criminal intermediaries and cyberattacks targeting critical infrastructure such as power stations.

He also stressed that the security landscape has changed significantly since 2001. Many essential systems and services are now operated by private companies, meaning governments cannot address emerging vulnerabilities on their own.

According to McCallum, governments, businesses and academic institutions need to work together to identify weaknesses and establish clear responsibilities before a crisis occurs. He warned that authorities should not wait until another major security incident to determine who controls a vulnerable system, who has the power to respond or who is responsible for raising the alarm.

The MI5 chief’s comments came as the world reflected on the September 11 attacks, when al-Qaida militants hijacked passenger aircraft and crashed them into the World Trade Center in New York and the Pentagon, killing thousands of people.

McCallum said remembering the victims should also involve preparing for future threats. He called for greater resilience and a willingness to adapt before the next major security shock occurs, rather than relying solely on lessons drawn from previous attacks.