PARIS — New laws make it easier to seize passports. Suspected fighters are plucked from planes. Authorities block finances and shut down radical mosques.
In cyberspace, Silicon Valley firms are wiping extremist content from websites, such as video of the recent beheading of two American journalists. And Western intelligence agencies are exploring new technologies to identify returning fighters at the border.
Governments from France to Indonesia have launched urgent drives to cut off one of the Islamic State group's biggest sources of strength: foreign fighters. At the heart of the drive is mounting concern that the organization is training the next generation of international terrorists.
Those fears have gained urgency from the group's horrific methods: A British militant is suspected of beheading two American journalists, and a Frenchman who fought with the Islamic State group is accused in a deadly attack on a Jewish museum in Belgium.
With each video that ricochets around social networks, the militants gain new recruits.
"If neglected, I am certain that after a month they will reach Europe and, after another month, America," Saudi King Abdullah said Friday, calling for a strong international response to the onslaught in Syria and Iraq.
After video emerged online of the killing of an American journalist last month, tech companies drafted plans to scrub the web of such content, and implemented them this week after a second beheading, a Silicon Valley insider said Wednesday. YouTube and Twitter accounts were among those shut down.
Islamic State militants who have migrated to Diaspora, a decentralized social network, are in many cases greeted with banners saying they are unwelcome. But they will find newly sophisticated ways to get a message out, according to Jamie Bartlett of the Demos think tank.
Britain has taken a particularly active role in censoring content deemed to break the country's strict rules against extremist propaganda. U.K. officials recently revealed they have been granted "super flagger" status on sites such as YouTube, meaning their requests to remove videos with grisly content or that encourage terrorism are fast-tracked.
Over the past four years, an Internet-focused counter-terror unit of London's Metropolitan Police instigated the removal of 45,000 pieces of content, the force said last week. Islamic State militants, however, have just as quickly found other, more decentralized platforms.
In the United States, officials are trying to identify potential jihadis by comparing travel patterns with those of people who have already joined the fight, a counterterrorism official said, speaking only on condition of anonymity because he was not authorized to discuss intelligence matters.
A French law to seize passports is being fast-tracked through parliament, and the government is ramping up arrests of increasingly young teenagers making plans for jihad.
That can mean last-minute arrests at the airport, as happened to a 16-year-old girl and her alleged recruiter trying to pass through security in Nice on Saturday, and to a man at Australia's Melbourne Airport who was pulled off a flight last week carrying tens of thousands of dollars in cash and the Islamic State group's black-and-white flag in his luggage.
Britain proposed laws Monday to let police seize the passports of those suspected of having traveled abroad to fight, while the Netherlands is making it easier to strip people of Dutch nationality and go after Internet providers that spread propaganda.
In Bosnia, authorities carried out a major anti-terror sweep on Wednesday. They detained 16 people suspected of fighting in Syria and Iraq and recruiting Balkan men to join Islamic militants there.
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