France is currently monitoring 12,000 people for signs of "radicalisation of a terrorist nature". It has announced a new strategy to tackle the problem - but will it help keep the country safe from attacks?
When you first meet her, Marie has a cautious, slightly untrusting manner. She speaks slowly, sketching thin outlines of her story - how she was radicalised, how she escaped - with challenge and vulnerability mixed together in her eyes.
The threat from those who recruited her is still very real and we've disguised her identity to protect her; Marie is not her real name.
"I was forced to pray," she said. "They tried to get me to adhere to their extremist religion, but I didn't take to it at all, so in punishment I was sexually assaulted."
Off camera, she confirms that she was raped.
"You have to stay silent," she says. "It's like playing cat and mouse - the mouse is in a very small box and the cat is ready to pounce at any time.
"You know that if you don't go along with them there will be sanctions."
Media captionWhat makes someone become an Islamic extremist? Jean-Claude Keller, who runs a de-radicalisation scheme, explains
The question of how to prevent people like Marie from falling under the influence of violent radical Islamist groups - and how to help them when they do - is something France has struggled with.
Full coverage of 2015 Paris attacks
Which countries have fleeing IS fighters gone to?
Inside France's 'boot camp' for wavering radicals
Pressure to combat extremist ideology grew after several major terrorist attacks here in 2015 and 2016, and recent military success against jihadist groups in Iraq and Syria - and the return of fighters to France - has turned the spotlight on radical networks at home.
Image copyright Reuters
Image caption Busy restaurants, bars and a concert hall were targeted in Paris in November 2015 in an onslaught that shocked France
Alongside the internet, prisons have been seen as a prime recruiting ground.
Marie says she was recruited in prison while serving time for an unrelated offence. "I was an easy target," she said. "I was far from my relatives, and I was lost, really lost."
Bad choices
The new deradicalisation strategy announced by the government includes the segregation of radicalised prisoners in separate wings.
But critics say it could prove dangerous, surrounding jihadist leaders with a hand-picked audience of potential recruits.
Image copyright AFP
Image caption Fleury-Merogis prison has a specialised unit for radicalised detainees. Paris attacks suspect Salah Abdeslam has been among them
"Of course, the radicalised detainees will cross paths and meet, but that's not the point," said Youssef Badr, a spokesman for the justice ministry.
"The real work we'll be doing is talking to them, challenging their contradictions. Each detainee will get individual treatment, and one-on-one meetings with case workers and chaplains."
The new plan also emphasises a need to combat the propaganda many young people access online.
A video released recently by the government is called You Always Have A Choice.
It is set in a run-down city suburb and shows a character facing a series of choices, each of which takes him down the path to radicalisation.
Image caption The person watching the interactive government video must choose what to do at key ethical crossroads
By the end of the video, after a run of bad choices, the character is arrested just as he's about to stage an attack.
But understanding why some people make the choices that lead them into extremist violence has provoked fierce debate in France - with some seeing it as a problem of religion, or law enforcement, while others say it is rooted in social divisions, isolation and lack of opportunity.
'Jihad academy'
It is a challenge many countries face. In the UK, successive governments have taken a broad approach, under the Prevent scheme, to tackle the spread of extremist ideology.
In France, there has been a slew of different measures including a hotline number for families to report their concerns, closed rehabilitation centres, and new powers for police.
But the government's approach has been criticised in the past as unfocused and ill thought out - one high-profile rehabilitation centre was nicknamed "jihad academy".