Ken McCallum called Russia, which denies involvement in hostile acts in Britain and other Western countries, “aggressor number one”. He said it was escalating “hybrid” warfare.

MI5 spy chief Ken McCallum delivered his annual speech on Tuesday outlining his view of the threats to Britain, from hostile states such as Iran and Russia to the development of artificial intelligence.

Here is a summary of the main threats and issues he detailed in his speech and subsequent questions from media:

RUSSIA

McCallum called Russia, which denies involvement in hostile acts in Britain and other Western countries, “aggressor number one”. He said it was escalating “hybrid” warfare, staying below the threshold that would trigger a direct NATO response.

He said Russia’s capabilities had been reduced by the expulsion of 1,000 officials from embassies since the invasion of Ukraine, which meant it had to rely on native volunteers and criminal proxies.

IRAN

Tehran is also using criminal proxies – to target opponents, Iranian media organisations and Israeli interests in Britain – and has expanded its hybrid campaign in the last year, McCallum said.

He said operations connected to Iran had yielded more than 50 arrests in the UK, and that many had been aimed at Jewish communities.

The other shift had been “Iranian ambitions to come at harder targets, like military sites”, he said.

Tehran also rejects accusations of malign activity in Britain.

ARTIFICIAL INTELLIGENCE

McCallum said AI was “supercharging the cybersecurity contest between attackers and defenders”, producing tailored propaganda and material for individuals.

MI5 has caught potential attackers using it to try to improve reconnaissance and attack methodologies. AI-enabled drones added a new challenge, he said.

McCallum said the greatest concern about the misuse of AI was terrorists developing bioweapons or even creating new pathogens.

AI also presented a risk in itself.

“Put at its simplest, human history has given us no experience of facing an actor which is smarter than we are, is capable of out-thinking us. This is genuinely novel and deserves the serious attention it is getting.”

TERRORISM

Britain in April raised its national terrorism threat level to “severe”, meaning an attack within the next six months is highly likely.

McCallum said Al Qaeda and Islamic State continued to inspire plots, and MI5 was still having to respond to attempts to carry out mass-casualty attacks.

He said the most marked trend of the last year had been the increase in cases where extreme anti-immigration and anti-Muslim grievances were tipping over into terrorist intent.

An investigation into one 13-year-old who had been radicalised by extreme right-wing ideology had led to an unnamed foreign partner thwarting a lethal attack on its soil, he said.

BREXIT

On Sunday, Prime Minister Andy Burnham said Russia had interfered in Britain’s 2016 referendum vote to leave the European Union, something Moscow has denied.

Asked about such interference, McCallum said it was public knowledge that Russian media such as Russia Today “came in pretty strongly around the time of the referendum”, and there had been a certain amount of activity from trolls and bots.

But he said Russian online trolling had been comparatively unimpressive.