Three-quarters of those who become foreign fighters for the Islamic State extremist group are recruited through friends and 20 percent through family members, a terrorism expert said Tuesday.

Scott Atran, co-founder of the Center for the Resolution of Intractable Conflict at Oxford University, said research has found that "radicalization rarely occurs in mosques" and very, very rarely through anonymous recruiters and strangers.

He said some Islamic State recruits come from Christian families "and they happen to be the fiercest of all the fighters we find."

Atran told a meeting held Tuesday on "Foreign Terrorist Fighters" organized by the U.N. Security Council's counter-terrorism committee that "it is the call to glory and adventure that moves these young people to join the Islamic State" and that "jihad offers them a way to become heroes."

The New York-born anthropologist said the Islamic State group has a "revolutionary pull," as occurred in the French Revolution, the Bolshevik Revolution in Russia, and the rise of Nazi Germany.

"The Islamic State represents the spearhead of the most dynamic counter-cultural revolutionary movement since World War II with the largest volunteer fighting force since World War II," he said.

Atran, who has interviewed captured fighters from the Islamic State and the al-Qaida linked Nusra Front, said leaders of the Islamic State group "understand youth much better than the governments that are fighting against them."

They know how to speak to the rebelliousness and idealism of youth, he said, and they are very adept at using social media to target young people 15 to 24 years old.

The West's counter-messaging that the Islamic State is bad, cuts off heads and wants to control women isn't intimate, effective, or universal, said Atran, who is also research director in anthropology at France's National Center for Scientific Research in Paris and holds academic posts in the United States.

He warned that unless the United Nations or other organizations "figure out how to have ideas from youth bubble up and be used to attract other youth, I think we'll be lost for the coming generations."

While those recruited to the Islamic State are often said to have "moral failings" or be "brainwashed," Atran said most foreign fighters who join the group, especially those from Europe, do so willingly.

He stressed that the Paris attacks that killed at least 130 people are an integral part of the Islamic State group's game plan.

"There is no change in the game of the Islamic State," he said. "This has been the plan and will continue to be the plan."

Their playbook includes hitting soft targets everywhere because it's impossible for nations to defend cafes, theaters and stadiums, Atran said. Their plan also includes drawing the Western powers into the Middle East again because "it will only cause chaos," and driving a wedge between Muslims and non-Muslims.

He said the 9/11 attacks in the United States in 2001 cost al-Qaida between $400,000 and $500,000 — and "we've spent between $4 trillion and $5 trillion" in the military and security response.

"Thus far, we are worse off than before and if we continue in this way we will be worse off still," Atran said.