What MI5 Says About Security Threats Facing the UK

What threats did MI5 identify?

MI5 chief Ken McCallum said the service is facing a heavier workload from hostile states than at any point since the Cold War. He said state-threat and terrorism work now take up roughly equal operational effort, as threats from foreign adversaries have increased sharply. ¹

He named Russia as the leading state concern and also warned about Iran. The speech also covered terrorism, including activity linked to the extreme right. These are different kinds of risk: state threats involve actions by or on behalf of governments, while terrorism involves violence pursued for political or ideological aims. ¹

What does MI5 say Russia is doing?

McCallum described Russia as using hybrid warfare: a mix of pressure and disruptive activity that can fall short of open military conflict. He said Russia seeks to unsettle European countries while avoiding actions that would trigger a joint response from NATO, the military alliance. He also said Russia had not moved into conventional conflict with the alliance. ¹

On the 2016 Brexit referendum, McCallum said Russia attempted to influence public discussion through pro-Brexit coverage on RT and Sputnik and through online troll accounts. He said there was no evidence that those efforts changed the outcome. The reported statement confirms an attempted influence campaign, not that the vote result was altered. ²

How could AI affect security in the UK?

McCallum said MI5 had caught terrorists seeking to use AI. He warned that the technology could support reconnaissance—gathering information about a target—and improve methods of attack. One concern is AI being combined with drones. ¹³

He also raised the possibility that AI could change the risks associated with biological weapons. A bioweapon is a weapon that uses disease-causing organisms or toxins. These are warnings about potential misuse; the sources do not describe a specific AI-enabled attack in the UK. ¹³

Could these threats affect everyday services?

The Independent reported McCallum’s warning that adversaries could disrupt essential services, including banking, flights and healthcare. The sources provide no details about a particular planned disruption, its likelihood, or a timeline. ³

The practical point is that national security concerns can involve both physical attacks and interference with services people rely on. The available reports describe MI5’s assessment and its work with other intelligence agencies, but do not offer individual steps for readers to take. ¹³

What is known about the Brexit interference claim?

McCallum said Moscow made an effort to influence the Brexit referendum debate through Russian broadcasters and internet trolls. He also said there was no evidence that the effort swayed the result. He did not present new evidence publicly, according to the Guardian’s report. ²

That distinction matters: evidence of an attempt does not by itself show that the attempt succeeded. The report does not quantify the campaign’s reach or establish how many voters, if any, changed their views because of it. ²

What is still uncertain?

The reports do not provide public details on the specific terrorist cases in which AI was allegedly exploited, or on the precise capabilities involved. They also do not quantify the probability or likely scale of future AI-assisted attacks. ¹³

For the Brexit claim, McCallum said no evidence showed that Russian efforts changed the result, but the report does not supply a detailed public assessment of the campaign’s effects. More generally, the sources report warnings rather than a full account of classified intelligence behind them. ²