MI5 chief warns: the next major security shock may come from somewhere we are not watching

LONDON — MI5 Director General Ken McCallum has warned that security services must avoid preparing perfectly for yesterday's threat while overlooking the completely different danger that could produce the next strategic shock.

Writing on the 25th anniversary of the September 11 attacks, McCallum said intelligence organisations must accept that the next major attack or security crisis will, by definition, not necessarily resemble 9/11. He warned that authorities could become too focused on known patterns and fail to identify a danger developing somewhere they are not currently looking.

Importantly, McCallum did not announce that MI5 had discovered a specific new 9/11-scale plot.

His warning was broader.

Al-Qaeda has been weakened but remains a threat, he said, while other militant groups continue to seek mass-casualty attacks. He cited the recent disruption of an Islamist plot targeting Manchester's Jewish community as evidence that terrorism remains an active concern.

But the modern security environment is far wider than terrorism. MI5 increasingly confronts state-backed activity ranging from cyberattacks to sabotage carried out through criminal proxies. McCallum specifically highlighted threats against power stations and essential infrastructure.

This challenge is complicated by the fact that much of Britain's critical infrastructure is now owned or operated by private companies. Telecommunications networks, energy systems, data centres and technology platforms cannot be protected by intelligence agencies acting alone.

His message was therefore partly organisational: government, businesses, universities and infrastructure operators need to know before a crisis who owns the risk and who has authority to respond.

Coming immediately after revelations about a suspected Russian operation around Arctic subsea cables, the warning has additional resonance.