North Yorkshire Police said criminals were claiming to have footage of their targets watching pornography and then demanding payment not to release the "footage".
The criminals have even been adding the person's password to the e-mail to make it appear genuine, the force warned.
What is sextortion?
Sextortion is a form of webcam extortion. Demands are made for money after victims engage with strangers - potential offenders - who use chat applications, the internet and a webcam.
The extortion takes place when those strangers persuade a victim to remove their clothes in front of their webcam and/or perform sexual acts. The victims believe this to be a private act – but it is not. The offender, unbeknown to them, is recording everything that they do.
Very soon afterwards, the offender will threaten them. They may demand money or publicise the video via YouTube or the victim's Facebook contacts.
Sextortion is a global problem and can occur anywhere the internet is accessible.
How to stay safe
North Yorkshire Police says many people think about their password or keeping device security up-to-date, but they should also consider:
What about what you are doing?
Do you really know who you are engaging with?
Is that person really who they say they are?
Is that person really 16, good looking and living where they suggest?
What is Remote Access Trojan (RAT)?
This refers to a webcam-based scam where malware is installed onto a victim's computer and can be used to operate their own built-in webcam, recording images of without their knowledge. This malware is known as a Remote Access Trojan (RAT), and can remotely activate a webcam, at the same time disabling the camera indicator light.
Keeping your computer security protection maintained and confirming that your web cam is de-activated when not in use should prevent this occurring. Some people have created a cover that can be placed over the camera for double protection.
What advice do the police have to share?
North Yorkshire Police has published the following tips to help people avoid becoming the victim of sextortion:
Be sensible when using the internet – it is in your hands. Only activate your camera when you want to. Make sure it is ‘off’ at all times when not required. Never allow yourself to be duped into activity that you will later regret.
If using Skype be alert to the fact that ‘contacts’ are not always who they say they are. If you allow a relationship to develop be guarded if unusual requests are made of you.
If you use online chat rooms looking for a person to chat with – be careful about any relationship that you form and in particular if you are asked to transfer to Skype.
Some online chat rooms have a visual contact facility so if you are looking for a person to chat with and allow a relationship to form – be guarded on what you say and do.
Relationships are quick to develop. End any that you are not comfortable with – stay in control of what you do.
If you make a mistake, you have doubts or you need support or advice – contact the police or a support agency immediately.
REMEMBER – what goes on the internet stays on the internet – for ever.
Where is more more help and advice available?
The force said that it is normal for people to feel embarrassed, fearful and even vulnerable if they have made a mistake online, but those who have made an error of judgement are not alone in doing so.
It said there are professionals who can help and offer support in a sensitive manner - but people need to report the matter first.