The hackers use malicious mobile apps to steal personal data and intercept text messages and phone calls.

According to Trend Micro, for a while now cybercriminals routinely make fake profiles on social media networks posing as attractive women to lure victims, and then persuade them to move onto a platform where there is video capability where they are recorded.

But the latest trick is to pretend to have audio problems during the conversation, and then persuade the victim to switch to an Android device and download a fake chat messenger app that the hacker prefers to use.

The chat app steals all the contact information stored on the victim's mobile device and sends it to the hacker. This information can in turn be used to scare the victim even further, by threatening to show the video to the victim's family, friends and colleagues, if the victim doesn't pay up.

"Mobile sextortion is prominent in South Korea though a case was also seen in Japan," the researchers write in their report. "In-depth investigation on various sextortion scams led us to developers in China tasked to create malicious apps and sites using Chinese and Korean."

The researchers discovered no less than 26 different malicious apps that included the keywords "voice support" and "security authentication".

There were also fake apps masquerading as private messaging apps, such as Just the Two of Us and Single Talk, as well as photo apps like My Photo Box 2.0 Beta and Gallery 2.0 Beta.

"The sextortion schemes we uncovered are complex operations that involve people across cultures and nations working together to effectively run a very lucrative business," the researchers concluded.