MI5 Chief Sir Ken McCallum said the UK intelligence service is now devoting more resources to countering state threats than during the Cold War, as foreign adversaries quadrupled their hostile activity over the past decade.
Russia ranks as "aggressor number one," McCallum told reporters at MI5's London headquarters. The Kremlin has abandoned conventional military action against NATO in favor of hybrid warfare, including cyber-attacks, sabotage and misinformation campaigns designed to destabilise European nations. Russia's full-scale invasion of Ukraine has made minimal progress at "horrifically costly" expense, McCallum said.
MI5 has expelled nearly 1,000 Russian spies from the UK since the invasion began, leaving Moscow dependent on paying criminal proxies to conduct attacks. "These are not the actions of a great power with the strategic upper hand," McCallum stated.
Iran has expanded hybrid operations in the UK, with 50 arrests related to Iranian activities in the past year. Much of that aggression targets Jewish communities and military sites. McCallum did not directly name RAF Fairford, a Gloucestershire airbase where three suspicious vans were parked and seven people were arrested and bailed by counter-terrorism police, but told reporters the incident "is not unique" and said "we have seen Iranian interest beyond RAF Fairford."
Countering terrorism now ranks as roughly equal in scale to state threat work, a shift McCallum described as "huge" in recent years. The April 2024 decision to raise the UK terrorism threat level to severe for the first time in five years reflected increased risk from both Islamist groups like Al Qaeda and Islamic State, and from extreme right-wing extremism. McCallum said extreme right-wing terrorism has "skewed young" and driven by internet radicalisation, with MI5 recently investigating a "radicalised extreme right-wing 13-year-old."
AI poses emerging threats McCallum called "unknown." Terrorists have used the technology to improve reconnaissance and attack planning, including AI-enabled drones. The most serious concern involves extremist groups potentially using AI to develop bioweapons, though McCallum said this threat remains "not yet realised." MI5 launched an AI Threat Assessment Centre to separate credible risks from speculation.