Researchers investigating mobile applications for Google Android smartphones have uncovered an app which surreptitiously records user’s phone calls and transmits them to hackers.

The unnamed ”Trojan  app” was identified by security experts at CA Technologies as one of the most invasive they had ever encountered and warned that it was an increasing trend on the platform – which subjects its developers to little vetting.

Once downloaded all calls the user makes are saved as a voice file on the phones memory, where it can be accessed by the malware’s makers.

Google pointed out that the app is not downloadable from the Android Market; users must seek out off-Market apps and accept permissions for access to outgoing phone calls for the trojan to work.