The new director of GCHQ has said that technology companies and certain web sites are effectively aiding terrorism.
Robert Hannigan, who is just 24 hours into his new role, joined GCHQ from the Foreign Office, but has experience of working with the agency.
He said that agencies and governments, like those of the UK and the US, struggle to cope with terrorism, and that technology companies could do more to help.
"The challenge to governments and their intelligence agencies is huge, and it can only be met with greater co-operation from technology companies," he told the Financial Times.
Hannigan said that terrorists no longer need to use anonymising methods, and that Islamic State (IS) operatives have adopted social engineering and hashtags to spread as many as 40,000 messages a day.
"Whereas al-Qaeda and its affiliates saw the internet as a place to disseminate material anonymously, or meet in ‘dark spaces', IS has embraced the web to promote its cause, intimidate people and radicalise new recruits," he added.
"There is no need for today's would-be jihadis to seek out restricted websites with secret passwords: they can follow other young people posting their adventures in Syria as they would anywhere else."
Technology companies are often accused of making it easy for terrorists to use the dark side of the internet. Google, for example, is often criticised for its response to piracy and requests for content removal.
Hannigan accused technology vendors of pitching certain services as "Snowden approved", making the enforcement task much more difficult.
"Techniques for encrypting messages or making them anonymous which were once the preserve of the most sophisticated criminals or nation states now come as standard," he said.
"These are supplemented by freely available programs and apps adding extra layers of security, many of them proudly advertising that they are ‘Snowden approved'. There is no doubt that young foreign fighters have learned and benefited from the leaks of the past two years."
Hannigan wants more support from the tech industry for GCHQ, MI5 and the Secret Intelligence Service, and expects the larger US providers to step in and assist.
"GCHQ and its sister agencies cannot tackle these challenges at scale without greater support from the private sector, including the largest US technology companies which dominate the web. I understand why they have an uneasy relationship with governments," he added.
"However much they may dislike it, they have become the command-and-control networks of choice for terrorists and criminals, who find their services as transformational as the rest of us.
"If they are to meet this challenge, it means coming up with better arrangements for facilitating lawful investigation by security and law enforcement agencies than we have now."
Hannigan believes that citizens will appreciate this assistance from the technology community.
The Open Rights Group (ORG) disagrees, however, saying that if the technology companies are slow to align themselves with the government it is because they are trying to protect their users and their users' privacy.
"Robert Hannigan's comments are divisive and offensive," said ORG executive director Jim Killock.
"If tech companies are becoming more resistant to GCHQ's demands for data, it is because they realise that their customers' trust has been undermined by the Snowden revelations.
"It should be down to judges, not GCHQ nor tech companies, to decide when our personal data is handed over to the intelligence services.
"If Hannigan wants a 'mature debate' about privacy, he should start by addressing GCHQ's apparent habit of gathering the entire British population's data rather than targeting its activities towards criminals."
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