Social networks should be proactively monitoring their users and informing authorities about any who cause particular concern, the director-general of MI5 said on Thursday morning.
During a live interview on BBC Radio 4's Today programme – the first ever given by an MI5 chief in the agency's 106-year history – Andrew Parker said that as social media services such as Twitter and Facebook blocked accounts for content tied to terrorism or child sex offences, they should also be turning over such users' information to governments.
The intervention is the latest in a mounting row between US and UK governments and many of the world's leading technology companies, who adopted much stronger encryption of users' data in the wake of revelations of government surveillance based on documents leaked by Edward Snowden.
A report by parliament's Intelligence and Security Committee last year on the murder of Lee Rigby by two extremists said that the death might have been preventable if intelligence agencies had been aware of postings by one of the killers to Facebook. Responding to a question on that report, Parker said social media giants had a moral duty to monitor their users.
"I think it goes to the question of the ethical responsibility of these companies for the communications and the data that they hold and they carry, and this question comes up in the realm of child sexual exploitation, terrorism, [and] other forms of crime," he said.
"Some of the social media companies operate arrangements for their own purposes under their codes of practice which cause them to close accounts sometimes because of what's carried," he continued, when pressed as to whether such arrangements amounted to handing intelligence agencies' responsibilities over to tech companies.
"I think there's then a question about, why not come forward. If it's something on sex exploitation or some other appalling area of crime, then why would the company not come forward?"
Parker also said greater cooperation from social media and technology companies was essential to preventing terrorists "going dark" – a term used for when people previously monitored by agencies are lost, generally because they start using more secure, encrypted, communication channels.
US and UK agencies had both previously suggested encryption backdoors would be a desirable solution to this problem, but the Washington Post revealed this week the USA's National Security Council had changed its position and was no longer calling for weakening encryption.
Parker – who was not asked directly about any of the Snowden revelations during the 25-minute interview – made no comment in either direction on encryption, but tackled "going dark".
"I think that is a very serious issue. It requires that there's a legal framework to authorise, but it also requires the cooperation of the companies who run and provide services over the internet that we all use," he said, "and it's in nobody's interests that terrorists should be able to plot and communicate out of the reach of any authorities with proper legal power."
Elsewhere in the interview, Parker said his agency had helped foil six terror threats in the last 12 months – "the highest number I can recall in my 32-year career". While MI5 was monitoring the arrival of refugees from Syria for any extremists, he said, it was not the "main focus" of where the UK's current terror threat originates.
Parker refused to be drawn on what provisions he wanted in the government's forthcoming new surveillance bill, intended to update the UK's ageing legal framework governing surveillance agencies. The MI5 chief refused twice to comment on whether he was opposed to judicial oversight of his agency.
Parker did, however, say his agency operated legally, with clear accountability, and only spied on those who posed a direct threat.
"It's a fundamental point that we operate in a framework of law set by parliament and overseen independently," he said.
Parker also tangentially addressed the core allegation of many privacy groups about the UK's approach to surveillance, which rests on collecting data in bulk through internet taps in order to find specific targets of surveillance interest. The UK's agencies contend this does not amount to mass surveillance as only a tiny portion of material collected is ever seen by a human, which privacy advocates reject.
"We do not have population-scale monitoring or anything like that," he said.