Security researchers from Zscaler report about a new type of ransomware for Android that poses as a porn app. The app promises access to free porn videos, but when users fire up the app it secretly take a photo of its user. The app then displays this image on a ransom page, which attempts to blackmail the victim into paying $500 to unlock the phone. More info and removal instructions can be found at Zscaler's blog.
This ransomware acts as a porn app named "Adult Player" and lures victims who assume it is a pornographic video player. When the victim starts using it, the app silently takes a photo of the victim, which is then displayed on the ransomware screen, along with the ransom message. The app demands a ransom of 500 USD.
To avoid being victim of such ransomware, it is always best to download apps only from trusted app stores, such as Google Play. This can be enforced by unchecking the option of "Unknown Sources" under the "Security" settings of your device.