Terrorists could harness artificial Intelligence to create destructive bioweapons, the head of MI5 warned, as he launched a new spy-led AI Threat Assessment Centre to assess the risks of the emerging technology.
Biological weapons – often shortened to “bioweapons”- are disease-causing agents, such as bacteria, viruses, fungi, or the toxins they produce, which are used to deliberately harm or kill people, animals, or crops. They work by spreading illness rather than through explosive force.
Sir Ken McCallum, director general of MI5, sounded the warning while giving his annual threat update in a speech at the agency’s London headquarters. He also warned Prime Minister Andy Burnham not to amplify the work of Russian trolls during the Brexit referendum for fear of doing their work of sowing discord for them.
“Many terrorists would dearly love to have some kind of capability of getting [a] biological or meteorological weapon. This is not yet manifest. But one risk is that AI could allow dangerous knowledge to get into their hands,” McCallum said, warning even “comparatively low sophistication actors may have a capability.”
New AI Threat Assessment Centre
The new AI Threat Assessment Centre (AITEC) will combine information from spies and open sources to “separate the bluster from the realities” to seek “both to seize the huge opportunities of Al and manage the risks thrown up by its misuse,” he said.
Last month Anthropic said it identified and disrupted attempts to use its AI model for “malicious activity” which could support the development of biological weapons, including an attempt to use its AI tool, Gemini, to obtain a “complete, step-by-step technical guide for synthesizing weaponised biological agents”.
General Sir Richard Barrons, who co-authored a root-and-branch review of Britain’s defence capabilities, told The i Paper earlier this year that “scary” advances in AI could help hostile states or actors more easily develop pathogens that could even target people.
A report last year by the authoritative Center for Strategic and International Studies (CSIS) warned that in one scenario, an existing pathogen such as a strain of avian influenza – which has a high fatality rate in humans but cannot currently transmit between people – could be adapted to spread more easily between humans.
The report warned: “Imagine, for instance, bird flu: Some strains have a reported human mortality rate of more than 50 per cent, meaning that approximately one out of every two people that contract the disease will die.
“Such a scenario would likely make the Covid-19 pandemic – which has claimed more than 27 million lives and shaken the world economy – look like the common cold.”
Sir Keir Starmer’s government published a new UK Biological Security Strategy in 2025 which acknowledged that “rapid developments in AI-enabled scientific tools and engineering biology offer significant opportunities for drug discovery and vaccine development, but also have the potential to introduce new risks of misuse”.
MI5 warning on Brexit wars
The day after Burnham was mired in a political row about the extent of Russia’s involvement in the 2016 Brexit referendum. Burnham said Russia did interfere with the Brexit referendum only for his own minister to clarify that there had been no fresh evidence since Parliament’s Intelligence and Security Committee found the Kremlin had tried but failed to alter the result.
“It is openly on the record that Russia Today and Sputnik and other Russian media organisations came in pretty strongly around the time of the referendum and it is also a matter of open-source record that there is certain amount of interference potentially through trolls and bots.
“I agree strongly with what the Prime Minister said yesterday, we did see a hack and leak inside the 2019 general election,” McCallum said.
However, the head of MI5 warned the premier not to re-run old battles at risk of amplifying the Russian trolls and bots who sowed division at the time.
McCallum added: “It is dependent upon us how far we allow our various attitudes to define us and I’m a little bit worried that we all stay in this debate for another few days that the Russian trolls… they’ll be delighted.
“They are front-page news once again, despite the comparative un-impressiveness of much of what they do at all the points along the journey. I am a little bit anxious that we don’t play into our adversaries’ hands by making these trolls look 10 feet tall. That’s not our experience of them.”
Russia greatest threat to UK
In a wide-ranging speech McCallum named the greatest threat to UK security from Vladimir Putin’s Kremlin, after a cyber-attack on Polish energy infrastructure, an attempt to blow up a German cargo plane with an explosive-laden drone and a thwarted assassination plot in the US. A man was charged in the UK last month for allegedly preparing to sabotage a drone factory in Swindon.
“Russia remains aggressor number one, as Putin’s Kremlin continues to lash out at the UK and its allies,” McCallum said.
“The Russian military and intelligence services are once again escalating their attempts at hybrid warfare- being careful to stay below the NATO Article V threshold it would be foolish for them to cross. This means Russia is using tactics that stop short – though sometimes not much short – of conventional conflict.”
The MI5 chief said it is “no accident” that Russia is trying to unsettle other European homelands “at a time when their military progress in Ukraine is minimal and horrifically costly.”
“You might be surprised to know that in 2026, MI5 is devoting more resource to countering state threats than during the Cold War. Over the last decade, our state threats caseload has quadrupled.”
Iran threat leads to 50 arrests in UK
He also said that 2026 has seen the Iranians, like the Russians, “attempting to expand their hybrid campaign. Over the last twelve months, our Iran-linked operations have led to more than fifty arrests in the UK.”
The alleged terror plot at RAF Fairford is not unique, he said, adding that Iran is aiming to hit targets here and abroad.
He also warned that “extreme right-wing terrorism also continues to skew young, driven by the internet.”