“It is probably the most ethnically diverse, sociologically diverse, non-monolithic … foreign fighter problem we have seen, so far,” US Army Lt. Gen. Michael K. Nagata said.
Nagata, the director of the National Counterterrorism Center's Directorate for Strategic Operational Planning, was speaking at the Center for Strategic and International Studies in Washington, D.C., earlier this week.
He said there is an "inherent imprecision" in the exact numbers of foreign fighters, but around 40,000 individuals have been identified from at least 120 countries.
The solution which was much discussed at last month's anti-ISIS summit and again by Nagata is intelligence sharing.
“The most vivid challenge we now face is ensuring that the information and intelligence about the travel, the plans, the intentions and identities of foreign terrorist fighters are as broadly known as possible everywhere in the world,” he said.
Foreign fighters try to mask their travel, he said.
“They try to hide within … the free flow of people, goods and services around the world,” Nagata said. “ … So getting information and intelligence about the plans, intentions and travel of a foreign fighter is inherently difficult.”
Iraq’s elite Golden Forces captured at least a dozen foreign fighters in eastern Mosul’s Maamoun neighborhood in February. The military said many had Russian passports.
Russian President Vladimir Putin said more than 4,000 militants from Russia and another 5,000 from former Soviet Union states are fighting with extremists in Syria, according to Russia Today news.
Interpol, a contraction of "international police," joined the coalition last summer and reaffirmed its support at the anti-ISIS ministerial.
“It can take just one officer conducting a traffic check, passport control or random search to potentially break terrorism investigation or foil a plot, but only if they have the information they need to make the right call,” said its secretary general, Jurgen Stock.
The US-based NBC News published an investigatory report on Americans who had joined ISIS overseas.
“They fit no particular pattern,” NBC wrote. “Some are from poor Muslim immigrant families. Others had what can be described as privileged backgrounds.”
The 2016 report said US officials estimated that roughly 250 Americans have tried to join ISIS.
Communications between ISIS leaders in Syria and Iraq and their followers around the world are often done through the Internet.
After last month’s rampage in London which killed four people, officials in the UK were quick to say investigators needed access to encrypted communications, which Khalid Masood, the 52-year-old attacker utilized.
“We need to make sure that organizations like WhatsApp – and there are plenty of others like that – don’t provide a secret place for terrorists to communicate with each other,” Sky News reported Home Secretary Amber Rudd as saying.
After the Westminster attack, Rudd met with representatives from Google, Facebook, Microsoft and Twitter.
Social media accounts spreading ISIS propaganda are increasingly being censored.
Twitter announced in a statement last month it has suspended more than 636,000 accounts since the middle of 2015 — 376,890 of those in the second half of 2016 — as the company steps up efforts in cooperation with government to counter the “promotion of terrorism.”
That came after it said in February it had shut down what it called 125,000 ISIS-linked Twitter accounts since mid-2015.
Twitter has acknowledged in previous statements the difficulty in identifying pro-ISIS tweets through a “magic algorithm.”
"You may not make threats of violence or promote violence, including threatening or promoting terrorism," Twitter policy states.
