Story highlights New chief of UK spying agency says big tech firms must cooperate in fight against terror

GCHQ director Robert Hannigan says ISIS is skilled in the use of social media platforms

They "have become the command-and-control networks of choice for terrorists," he says

In the Financial Times, Hannigan says intelligence agencies face a huge challenge

UK spy chief Robert Hannigan called on big U.S. tech companies to do more to help governments combat terrorism Tuesday, as he described social media as "a terrorist's command-and-control network of choice."

In an opinion piece written for Britain's Financial Times newspaper, Hannigan, the new director of UK government eavesdropping agency GCHQ, said there must be greater cooperation from the private sector to tackle the threat.

His comments play into the continuing debate over the conflict between people's right to privacy online and governments' need to ensure national security, intensified by the revelations last year of former NSA contractor Edward Snowden over mass government surveillance programs.

In a rare public statement, Hannigan accused U.S. tech companies of being in denial over terrorists' use of the Internet.

"They are exploiting the power of the web to create a jihadi threat with near-global reach. The challenge to governments and their intelligence agencies is huge -- and it can only be met with greater co-operation from technology companies," he said.

Photos: Sharing secrets: U.S. intelligence leaks Photos: Sharing secrets: U.S. intelligence leaks Sharing secrets: U.S. intelligence leaks – John Walker ran a father and son spy ring, passing classified material to the Soviet Union from 1967 to 1985. Walker was a Navy communication specialist with financial difficulties when he walked into the Soviet Embassy and sold a piece of cyphering equipment. Navy and Defense officials said that Walker enabled the Soviet Union to unscramble military communications and pinpoint the location of U.S. submarines at all times. As part of his plea deal, prosecutors promised leniency for Walker's son Michael Walker, a former Navy seaman. Click through the gallery to see other high-profile leak scandals the United States has seen over the years. Hide Caption 1 of 10 Photos: Sharing secrets: U.S. intelligence leaks Sharing secrets: U.S. intelligence leaks – Military analyst Daniel Ellsberg leaked the 7,000-page Pentagon Papers in 1971. The top-secret documents revealed that senior American leaders, including three presidents, knew the Vietnam War was an unwinnable, tragic quagmire. Further, they showed that the government had lied to Congress and the public about the progress of the war. Ellsberg surrendered to authorities and was charged as a spy. During his trial, the court learned that President Richard Nixon's administration had embarked on a campaign to discredit Ellsberg, illegally wiretapping him and breaking into his psychiatrist's office. All charges against him were dropped. Since then he has lived a relatively quiet life as a respected author and lecturer. Hide Caption 2 of 10 Photos: Sharing secrets: U.S. intelligence leaks Sharing secrets: U.S. intelligence leaks – Jonathan Pollard is a divisive figure in U.S.-Israeli relations. The former U.S. Navy intelligence analyst was caught spying for Israel in 1985 and was sentenced in 1987 to life imprisonment. Previously, the United States and Israel discussed his possible release as part of efforts to save fragile Middle East peace negotiations, according to sources familiar with the talks. On July 28, 2015, Pollard's lawyer announced that the convicted spy had been granted parole and would be released on November 21 -- exactly 30 years after his arrest. Hide Caption 3 of 10 Photos: Sharing secrets: U.S. intelligence leaks Sharing secrets: U.S. intelligence leaks – Wen Ho Lee was a scientist at the Los Alamos Laboratory in New Mexico who was charged with 59 counts of downloading classified information onto computer tapes and passing it to China. Lee eventually agreed to plead guilty to a count of mishandling classified information after prosecutors deemed their case to be too weak. He was released after nine months in solitary confinement. Lee later received a $1.6 million in separate settlements with the government and five news agencies after he sued them, accusing the government of leaking damaging information about him to the media. Hide Caption 4 of 10 Photos: Sharing secrets: U.S. intelligence leaks Sharing secrets: U.S. intelligence leaks – Members of the Bush administration were accused retaliating against Valerie Plame, pictured, by blowing her cover in 2003 as a U.S. intelligence operative, after her husband, former Ambassador Joe Wilson, wrote a series of New York Times op-eds questioning the basis of certain facts the administration used to make the argument to go to war in Iraq. Hide Caption 5 of 10 Photos: Sharing secrets: U.S. intelligence leaks Sharing secrets: U.S. intelligence leaks – In 2007, Lewis "Scooter" Libby, Vice President Dick Cheney's former chief of staff, was convicted on charges related to the leak of the identity of CIA operative Valerie Plame. Libby was convicted of obstruction of justice and perjury in connection with the case. His 30-month sentence was commuted by President George W. Bush. Cheney told a special prosecutor in 2004 that he had no idea who leaked the information. Hide Caption 6 of 10 Photos: Sharing secrets: U.S. intelligence leaks Sharing secrets: U.S. intelligence leaks – Aldrich Ames, a 31-year CIA employee, pleaded guilty to espionage charges in 1994 and was sentenced to life in prison. Ames was a CIA case worker who specialized in Soviet intelligence services and had been passing classified information to the KGB since 1985. U.S. intelligence officials believe that information passed along by Ames led to the arrest and execution of Russian officials they had recruited to spy for them. Hide Caption 7 of 10 Photos: Sharing secrets: U.S. intelligence leaks Sharing secrets: U.S. intelligence leaks – Robert Hanssen pleaded guilty to espionage charges in 2001 in return for the government not seeking the death penalty. Hanssen began spying for the Soviet Union in 1979, three years after going to work for the FBI and prosecutors said he collected $1.4 million for the information he turned over to the Cold War enemy. In 1981, Hanssen's wife caught him with classified documents and convinced him to stop spying, but he started passing secrets to the Soviets again four years later. In 1991, he broke off relations with the KGB, but resumed his espionage career in 1999, this time with the Russian Intelligence Service. He was arrested after making a drop in a Virginia park in 2001. Hide Caption 8 of 10 Photos: Sharing secrets: U.S. intelligence leaks Sharing secrets: U.S. intelligence leaks – Army Pvt. Bradley Manning was convicted July 30 of stealing and disseminating 750,000 pages of classified documents and videos to WikiLeaks, and the counts against him included violations of the Espionage Act. He was found guilty of 20 of the 22 charges but acquitted of the most serious charge -- aiding the enemy. Manning was sentenced to 35 years in military prison in 2013. Hide Caption 9 of 10 Photos: Sharing secrets: U.S. intelligence leaks Sharing secrets: U.S. intelligence leaks – Former intelligence contractor Edward Snowden revealed himself as the leaker of details of U.S. government surveillance programs run by the U.S. National Security Agency to track cell phone calls and monitor the e-mail and Internet traffic of virtually all Americans. Snowden has been granted temporary asylum in Russia after initially fleeing to Hong Kong. He has been charged with three felony counts, including violations of the U.S. Espionage Act, over the leaks. Hide Caption 10 of 10

The extremists use such platforms as Twitter, Facebook and WhatsApp to reach their target audience in a language they understand, Hannigan said.

Their methods include making use of popular hashtags for other stories in the news, such as Ebola or the World Cup, to disseminate their message, he said. They create slick videos and have learned that showing the full extent of their brutality turns people off, he said -- hence their posting of videos of beheadings that stop short of showing the moment of death.

Information requests

Google, WhatsApp, Facebook and Microsoft have not yet responded to a CNN request for comment on the spy chief's call for more cooperation.

A public policy communications officer for Twitter, Nu Wexler, said the company was not able to break out how many of the requests for information made to it by governments relate to terrorism, but he said Twitter is suing the U.S. government for the ability to do so.

In the six months that ended on June 30, Twitter received 78 account information requests from the UK government, its Transparency Report shows . Some information was produced in 46% of those cases.

Over the same period, 61% of all worldwide requests for account information received originated from the United States , with 1,257 requests in total. Some information was produced in nearly three-quarters of cases.

'Noisy channel' for radicalization

Hannigan, who took the reins as GCHQ director on Monday , said that ISIS militants show an alarming ease with new media that presents a new challenge for authorities.

"Terrorists have long made use of the internet. But ISIS's approach is different in two important areas," he said.

"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."

If Britain's intelligence and security agencies are to combat this effort, private sector firms -- including the largest U.S. technology companies that dominate the Web -- must do more to facilitate lawful investigations, he said.

"I understand why they have an uneasy relationship with governments. They aspire to be neutral conduits of data and to sit outside or above politics," he said.

But, he said, "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."

The new generation of extremists is also helped by the additional encryption measures now widely available to users of the Internet and smartphones, Hannigan 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,' " he wrote.

"There is no doubt that young foreign fighters have learnt and benefited from the leaks of the past two years."

Recent efforts by Google and Apple to encrypt their latest smartphones in ways that would prevent law enforcement from accessing certain private data have alarmed the U.S. Federal Bureau of Investigation.

FBI Director James Comey told reporters in recent weeks that he was "very concerned" that the companies were "marketing something expressly to allow people to place themselves above the law."

'Lost insight'

A former top U.S. intelligence official also told CNN last month that ripping the cover off secret U.S. surveillance programs had pushed foreign terrorists underground and out of intelligence services' reach.

"We've lost collection against some individuals, people that we were concerned about we are no longer collecting their communications," said Matt Olsen, who until September led the National Counterterrorism Center. "We lost insight into what they were doing."

Snowden, whose massive leaks on intelligence-gathering programs resulted in espionage charges from the U.S. government, has been living in Russia for the past year.

In an interview in May, he said he had no choice other than leaking the highly classified information, since he believed the Constitution was being violated.