Iran is stepping up efforts to target more heavily protected sites, including military facilities in Britain, while Russia is intensifying hybrid warfare against Ukraine’s allies, MI5 Director General Ken McCallum warned on Tuesday.

In his annual speech on threats facing the United Kingdom, McCallum also highlighted the potential misuse of artificial intelligence (AI) to develop biological weapons and create new pathogens.

He said threats from hostile states had quadrupled over the past decade. MI5 now devotes more resources to countering them than it did during the Cold War.

UK Raises Concerns Over Suspected Iran-Linked Plot

The warning followed British Prime Minister Andy Burnham’s statement on Monday that Tehran was “highly likely” behind a suspected plot targeting RAF Fairford, an airbase used by US bombers involved in strikes against Iran.

The incident prompted a security alert and reportedly led US President Donald Trump to withdraw aircraft from the base.

Iran has denied involvement in the Fairford incident and rejected broader accusations of hostile activity in Britain. British authorities have previously accused Tehran of involvement in plots and attempted assassinations targeting dissidents and Israeli and Jewish interests.

The allegations add to concerns about state-linked threats in the UK. However, the claims surrounding the Fairford incident remain allegations and should not be treated as established findings.

MI5 Chief Describes Russia as Major Security Threat

McCallum also warned about Russia’s activities across Europe, describing Moscow as the “aggressor number one”.

He said Russia was using tactics that fall short of conventional warfare but could still disrupt and intimidate other countries.

Section 144 Imposed in Dera Ismail Khan Until November 11

McCallum cited an alleged attempted drone attack involving a cargo plane at Leipzig/Halle Airport in Germany in August and a cyberattack targeting Polish energy infrastructure.

“It’s no accident that Russian aggressors are trying to unsettle other European homelands at a time when their military progress in Ukraine is minimal and horrifically costly,” he said.

Russia has denied involvement in hostile activities across Western countries. It also rejected Germany’s accusations over the airport incident as “entirely fabricated”.

AI Could Increase Risks From Biological Weapons

McCallum said artificial intelligence was changing the cybersecurity landscape by strengthening both attackers and defenders.

He also warned that terrorists were exploiting AI to improve reconnaissance and develop attack methods.

However, he identified biological weapons as a particularly serious potential risk. He said AI could make it easier to misuse existing biological weapons or develop new ones.

“Not yet realised — the misuse case to which I’d attach greatest weight — is AI’s potential to change the stakes on existing or even new bioweapons,” McCallum said.

He added that the issue was receiving particular attention from him and his colleagues.

“These risks are real,” he said.

McCallum’s remarks highlighted three areas of concern for British intelligence: suspected state-linked threats from Iran, Russia’s hybrid operations against European countries and the potential for AI to increase the risks posed by biological weapons.