GCHQ's Robert Hannigan says tech firms 'in denial' on extremism

US technology companies have become 'the command and control networks of choice' for terrorism, the new head of GCHQ has claimed.

Writing in the Financial Times, Robert Hannigan says some US tech companies are 'in denial' about how their services are being misused.

He also said UK security agencies needed support from 'the largest US tech companies which dominate the web'.

Extremist groups in Syria and Iraq had 'embraced the web', he added.

'However much they may dislike it, [US technology companies] have become the command and control networks of choice for terrorists and criminals, who find their services as transformational as the rest of us,' Mr Hannigan says.

'The challenge to governments and their intelligence agencies is huge - and it can only be met with greater co-operation from technology companies.

'GCHQ and its sister agencies, MI5 and the Secret Intelligence Service, cannot tackle these challenges at scale without greater support from the private sector, including the largest US technology companies which dominate the web.'

Gordon Corera, BBC security correspondent

This is a hard-hitting article from the new GCHQ director in his first move on taking up the role. His aim is clear - to pressure tech companies to work more with government.

Following the Snowden disclosures last year, some of those companies have been less willing to share data with intelligence and law enforcement and more inclined to encrypt it - making it harder for authorities to gain access.

Tech companies may be surprised by the ferocity of the attack. And they - and privacy activists - may also argue that the spies started this fight with the scale of their intelligence collection and by hacking into some of those companies.

But Robert Hannigan has wasted no time in wading into the debate over security and privacy and making clear he will not shy away from a fight.

Mr Hannigan goes on to say that Islamic State (IS) , also known as Isil, has a different approach to using the internet than other terror groups have had.

'Where al-Qaeda and its affiliates saw the internet as a place to disseminate material anonymously or meet in 'dark spaces', Isis has embraced the web as a noisy channel in which to promote itself, intimidate people, and radicalise new recruits.'

He also says most internet users 'would be comfortable with a better and more sustainable relationship between the [intelligence] agencies and the tech companies'.

Hashtags strategy

Earlier in the year an investigation by the Guardian revealed how IS was using popular hashtags - including ones used during the Scottish Referendum - to boost the popularity of its material on Twitter.

Security minister James Brokenshire met recently with representatives from technology companies - including Google, Microsoft and Facebook - at a private dinner in Luxembourg to discuss ways to tackle online extremism.

The government's Counter Terrorism Internet Referral Unit (CTIRU), set up in 2010, has removed more than 49,000 - pieces of content that 'encourages or glorifies acts of terrorism' - 30,000 of which were removed since December 2013.

Scotland Yard's head of counter-terrorism Assistant Commissioner Mark Rowley has previously said that officers are removing more than 1,000 online postings a week, including graphic and violent videos and images.