A campaign to hack and jam Isis last year represented the first time that Britain has used its cyber capabilities as part of a joint military campaign, the head of the country’s electronic intelligence unit said.
Jeremy Fleming, the head of GCHQ, said cyber attacks had “made a significant contribution” to the war against the Islamist extremist group.
“This is the first time the UK has systematically and persistently degraded an adversary’s online efforts as part of a wider military campaign,” he said, in a speech to the CyberUK conference in Manchester.
“In 2017 there were times when Daesh found it almost impossible to spread their hate online, to use their normal channels to spread their rhetoric, or trust their publications.”
He added: “We may look to deny service, disrupt a specific online activity, deter an individual or a group, or perhaps destroy equipment and networks.
“Of course, the job is never done — they will continue to evade and reinvent. But this campaign shows how targeted and effective offensive cyber can be.”
Mr Fleming did not give any further details of the methods GCHQ was using to disrupt Isis operations.
But his remarks present the fullest picture any UK security official has given about the country’s cyber offensive capabilities since former defence secretary Michael Fallon revealed last June that Britain was “routinely” using cyber attacks against Isis.
In a report last December, the parliamentary Intelligence and Security Committee, disclosed how GCHQ has “over achieved” in cyber offensive operations, creating double the number of new offensive cyber capabilities than expected.
After 25 years with domestic security service MI5, Mr Fleming took over from Robert Hannigan last year, who unexpectedly left the agency citing personal reasons.
A career spy, it is not clear which direction Mr Fleming will take GCHQ. Under his predecessor the spying agency attempted to become more open and transparent in response to the 2013 leaks by the former National Security Agency contractor Edward Snowden.
But he faces a formidable set of challenges as tension between the west and Russia grow and other countries such as Iran and North Korea step up their own cyber offensive capabilities.
Mr Fleming said: “The Russian government widely uses its cyber capabilities. Whether that’s NotPetya against the Ukraine’s financial, energy and government sectors, which eventually spread across the world.
“Or the use of industrial scale disinformation to sway public opinion. They’re not playing to the same rules . . . they’re blurring the boundaries between criminal and state activity.”