Terrorists are hunting for fresh targets because there are fewer crowds amid the coronavirus pandemic, the new boss of MI5 has warned.

Director general Ken McCallum said the security service has been “rapidly adapting” how it works to keep the country safe during the outbreak as well as helping research efforts in combatting the virus and trying to protect work on the vaccine from potential interference.

Speaking to reporters on Wednesday for the first time since taking on the top role in April, he said: “I stepped into this role at the height of the Covid lockdown, and for MI5 just like everyone else, 2020 has been dominated by the pandemic.

“We’ve sought where we can to help on Covid itself – advising on the safe construction of Nightingale hospitals; repurposing research originally done on toxic chemicals to help understand how Covid in droplets might disperse in certain environments; offering our skills in data analytics and modelling; simply allowing medically-qualified MI5 officers to step away from their duties here and directly support our NHS.

“And, crucially, on the vaccine, we’ve been working to protect the integrity of UK research.

“Our larger task has been rapidly adapting how we perform our core role of keeping the UK safe.

“The big shifts in everyone’s lives – reduced travel, more online, and the rest – mean shifts in how our adversaries are operating.

“Fewer crowds mean terrorists look at different targets; online living means more opportunities for cyber hackers; and so on.

“Equally, 2020 has demanded shifts in how MI5 itself has to operate; you wouldn’t expect me to get into detail, but common sense will tell you that covert surveillance is not straightforward on near-empty streets.”

Mr McCallum, who is in his forties, became the youngest ever director general when he took over from Sir Andrew Parker, who retired after leading the organisation since 2013.

The maths degree graduate, who grew up in Glasgow, has been the deputy director general since April 2017 and has 25 years of experience at MI5 including work on Northern Ireland-related terrorism, Islamist extremism and cyber security.

His career has seen him take charge of the service’s response to the attempted assassination of former spy Sergei Skripal in the Salisbury nerve agent attack as well as leading the response to the 2017 terror attacks and taking charge of counter terrorism investigations and risk management surrounding the 2012 London Olympics.

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