Android smartphones are now threatened with malware disguised as anti-virus software that locks the desktop and tries to extort money to unlock it. Away from the Google Play Store, Symantec has discovered one such piece of malware which, like the BKA trojan, uses pornographic content to extort money from users. Even after the ransom is paid, the malware has embedded itself deep into the system and continues to annoy the user.

The Android ransomware markets itself as "Free Calls Update". IF it is installed, the malware confronts the user with a "trial version" of Android Defender (see video). It is not compatible with all phones, but if it finds one that is compatible, it launches the con.

The malware does not lurk in Google Play. It can only be found on alternative sources such as app catalogues, forums and file-sharing applications. To install apps from non-trusted sources, users have to activate what's known as sideloading. Users who only install apps from Google Play have little to fear.