Men using social networking and online dating sites are being targeted by fraudsters posing as attractive young women.
Victims are typically lured into taking off their clothes in front of their webcam allowing the fraudster to record a video.
A threat is then made to publish the video with false allegations of paedophilia unless money is paid.
French police say they are being told of incidents every day, with most probably going unreported.
One victim, a 28-year-old man, is willing to speak about his experience but wishes to remain anonymous.
"She sent me a message and I was happy because normally the girls don't take the first step," he says.
"She said she was French, living in Lyon, but was on holiday in Ivory Coast. We then chatted for a bit on MSN and I could see a video of her. She was a very beautiful French-looking girl, very pretty."
"She was dressed to begin with and asked whether I would be interested in going further. I asked what that meant and she said she wanted to see my body... everything.
"She put on another video and started to undress. I was completely taken in. I had no idea this was a video. I thought it was real.
But her real intentions soon became clear.
"After five minutes she sent me a message saying: 'Have a look at this video I've taken of you. I am going to put it on YouTube unless you send me some money.'
"I looked at the video - you could see my face... you could see everything."
On the same page, the victim saw many other similar videos of people entrapped in this way.
The blackmailer wanted 500 euros ($600) wired to Abidjan, the capital of Ivory Coast, or else the video would remain online.
It was captioned with the victim's name and the false allegation that he was performing a sexual act in front of a young girl.
French police have received a spate of reports of blackmail attempts fitting a similar description.
"At the moment we are persuaded that there are several blackmail attempts committed every day," says Vincent Lemoine, a specialist in cybercrime in the Gendarmerie's criminal investigations unit.
"Unfortunately, not everyone who finds themselves victims of this crime is coming forward to the police because these blackmail attempts are so intimate."
The French reputation management company, Reputation Squad, has received an alarming number of calls from lonely hearts after they were persuaded to reveal too much of themselves online.
"Most of the time the people that call us are really panicked and they don't know what to do and are very afraid it is going to ruin their entire life," says Alberic Guigou.
"So they come to us in despair and they always make up stories. They never say: 'I met someone on the internet and I went naked'.
"But 95% of the time it is actually webcam blackmail."
If initial attempts to extort payment fail, the men behind the beguiling internet mask finally reveal themselves, this time posing as agents from the Ivorian police.
"The blackmailers also post the video up on a false website purporting to be that of Interpol, the local police or the French police," says Vincent Lemoine.
"At the same time, they email false documents, which indicate to the person that they have committed acts of paedo-pornography and to bring an end to the affair they have to pay a fine."
I spoke to one woman whose ex-husband paid out around 3,500 euros ($4,250) to blackmailers in June this year.
His blackmailers were relentless and he could see no end to his ordeal. A week after the first demand, he killed himself.
Journalist for the Le Monde newspaper Laure Belot has spoken to people who never thought they would be a victim of this kind of scam.
"We can say what an idiot for undressing in front of a webcam but our society is a society of solitude where people are alone in their rooms with a computer during the night.
"For a person who is already alone, you can imagine that this is enormously destructive. If you have people around you who can help, that is great, but often these are people who are alone and it can be very dramatic. If you are very young, this can be devastating."
Alberic Guigou says: "People get the feeling that when something is out there on the internet it is going to stay there forever.
"Fortunately it is not always the case. And there are many, many cases in which you can intervene and get things removed from the internet, especially when it is pornography such as the webcam blackmail."
YouTube does not host sexually explicit content and should such a video be posted on their site it can be flagged as inappropriate and taken down.
French police advise victims not to meet the blackmailer's demands - the 28 year-old victim we spoke to refused to pay - his blackmailers lost interest and went away. Another victim who paid up, ended up being asked for more.
They also advise victims of webcam blackmail to report it to them or to at least signal it on their
Police have been investigating, but there is only so much they can do - current mechanisms for international co-operation between police are limited.
This sort of crime is only possible because of the unique connectability, anonymity and intimacy-at-a-distance which the internet affords.
Until the differences that separate international law enforcers are bridged as easily, we will continue with victims in one country, perpetrators in another - and with little that can be done about it.