The cyber operation hindered the group's ability to co-ordinate attacks and suppressed their propaganda, former MI5 senior officer Jeremy Fleming was quoted as saying by the BBC.
Fleming, speaking for the first time since becoming head of GCHQ in 2017, said: "These operations have made a significant contribution to coalition efforts to suppress Daesh (IS) propaganda, hindered their ability to coordinate attacks and protected coalition forces on the battlefield.
"The outcomes of these operations are wide-ranging," he told the Cyber UK 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.
"... 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.
However, Fleming said the fight against the IS was not over as the group continued to "seek to carry out or inspire further attacks in the UK" and find new "ungoverned spaces to base their operations".
Fleming also criticised Russia over what he called "unacceptable cyber-behaviour" which was a "growing threat" to the UK and its allies.
He said the Salisbury poisonings showed how "reckless" the Kremlin was prepared to be and accused Russian President Vladimir Putin of not "playing by the same rules".
But he said the UK could draw on a breadth of "excellence and expertise" within the intelligence services, military and police, both in the UK and with allies to help keep the nation safe.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
