Android's open source nature means developers have more freedom when submitting apps, including the ability to change code after installation. That issue has led to two apps with malware being available for two weeks, with one reaching 100,000 downloads.

The apps - copied versions of Super Mario Bros. and Grand Theft Auto 3 - weren't covered by Google's screen tool, called Bouncer. After installation the app downloaded an extra element called Activator which sent premium text messages that the user paid for in the following month's phone bill. Similar apps emerged recently, sending text messages in Russian to everyone in a user's contacts book.

Google removed the apps after being noted by security firm Symantec, but not before the apps had been downloaded between 50,000 and 100,000 times.

"What is most interesting about this Trojan is the fact that the threat managed to stay on Google Play for such a long time, clocking up some serious download figures before being discovered. Our suspicion is that this was due to the remote payload employed by the Trojan," Symantec said. "remote payload" refers to Activator, which is downloaded by the app connecting to a Dropbox account.

According to MSNBC, mainly Russian users were targeted where premium SMS scams are more common. Activator warns of sending out SMS messages after sending the messages.

Users who downloaded the app probably should have known that Super Mario is a Nintendo property and there isn't going to appear on non-Nintendo devices, especially mobile devices that compete with the Nintendo 3DS. It's the same case with Rockstar: Grand Theft Auto would have been announced in advance before arriving on Android or any other mobile device. The GTA app copies Grand Theft Auto 3, called "GTA 3 - Moscow City" - which originally launched on the PlayStation 2.

iOS had its own malware app on the Store, which sent the aforementioned Russian text messages. Recent issues caused around 120 apps - including notable apps such as Instagram - to crash when opened, which has since been fixed by Apple.