As jihadist attacks are increasingly being carried out by home-grown "lone wolves," top counter-terror chiefs of four Western powers said Thursday they need more support from social media companies to detect potential threats.

While traditional intelligence methods are foiling large-scale plots coordinated from abroad, the officials from the United States, Britain, Germany and Canada said that isn't enough to uncover attacks by self-radicalized individuals like those this year in Britain that have killed dozens.

Paddy McGuinness, the British deputy national security adviser for intelligence, said many countries are still too focused on foreign-derived attacks planned or directed by the Islamic State group or Al-Qaeda.

After the four attacks in Britain this year, he said at a Washington intelligence forum, "We are dealing with conspiracies that really do not involve an overseas element."

"We're dealing with a problem in our communities, with people who do not travel, and become radicalized and move to violence... These were British plots by British people."

Christian Rousseau, head of Canada's Integrated Terrorism Assessment Centre, calls it a shift to "Terrorism 3.0" as the Islamic State group reels from battlefield defeats in Iraq and Syria.

"The ability of an organized threat directed from overseas, where people travel, money travels, things travel, we're relatively good at being able to catch that," he told the Intelligence and National Security Summit in Washington.

"The generation of terrorism that is now most impactful in Canada is the inspired or enabled terrorism," he said. Those are people who self-radicalize or radicalize online, then decide to launch an attack.

"We're in a world that's even more difficult because not only can we not deter them... but there are no signs to help us deal with this."

In Germany, too, attacks trend toward self-radicalized, "inspired lone wolves," according to Friedrich Grommes, head of the international terrorism division of the German Federal Intelligence Service.

But in Germany's case these have been from recent immigrants, not second-generation immigrants like in Canada, Britain and the United States.

- More help from Facebook wanted -

The officials said that shift requires new approaches to detecting threats, with a focus on sources like social media.

But tough privacy laws and the protections enjoyed by the largely American internet and social media giants are impeding authorities in their ability to ferret out lone wolf threats, they said.

McGuinness said he wants to see more pro-active support from Facebook, Google and other online giants with the ability to conduct large-scale automated scanning of users for possible threats.

He also called on the United States to pass laws to lift a ban on US internet companies responding to terror-related search warrants from foreign law authorities.

More than 95 percent of crime and terror cases involve people using an American technology application, he said.

- Challenge of encryption -

Potential attackers and their Islamic State coaches usually move to the encrypted "dark web" to talk, Rousseau said.

"We can see the invitation, but we can't see the conversation afterwards," he said. "Encryption is stopping us from seeing the whole picture."

Even in Germany, where privacy protections are especially strong, there is increasing understanding of the need for more access by counter-terror investigators, Grommes said.

"ISIL is vanishing from the soil and going cyber," he said, referring to the Islamic State group.

"There is a growing understanding that we have to adjust our legislation to the European level... to assert the balance between protecting privacy and discovering illegal things like international terrorism."

Nick Rasmussen, director of the US National Counterterrorism Center, said American authorities are having more success by pumping large amounts of evidence of potential jihadist activity to the social media companies themselves, to press them to act unilaterally.

"We are going to make sure we burden them with knowledge about how their tools, their technologies, their platforms are being used," he said.