Researchers at Kaspersky Lab issued a report on the Koler ransomware, which is targeting both Android devices and desktop browsers. In May 2014, French researcher Kafeine, discovered new mobile malware named AndroidOS.Koler.a, the attack starts when victims will visit a pornographic website on their Android device, then they are redirected to a site which host a malicious.apk file used by criminals to lock the devices screen and. demands payment of a fee between $100 and $300.”]
Source: https://securityaffairs.co/wordpress/27113/cyber-crime/kaspersky-koler-ransomware.html