Android’s 2012 security overhaul hasn't stopped the volume of global threats targeting the mobile OS continuing to rise at an alarming rate, F-Secure’s latest mobile threat report has found.

The company noticed 51,447 unique Android malware samples in the third quarter, an unexpectedly huge jump from Q2’s figure of just over 5,000 and around 3,000 in Q1.

Each one of these files was a single instance of 67 malware variants and families the company identified as being active in the same period, which suggests that the rise is probably best explained as signalling that criminals are launching more attacks with roughly the same malware types to choose from.

According to F-Secure, Android's malware problem can be explained by its huge popularity across the world, coupled to high growth rates; Android’s market share in China – now the world’s largest smartphone market by units – is currently 81 percent, the company said.

In these countries, Google’s overhauled Play Store is only one among a diversity of sources for Android applications, a fragmentation wrinkle malware-distributors have been quick to exploit. People seem happy to download apps from third-party stes.

As F-Secure’s detailed list of malware examples illustrates, the majority of rogue apps are driven by simple SMS tariff fraud.

After a complacent start, Google has shown signs of getting on top of its embarrassing malware problem, first reinventing the Market as Play, a supervised single location for app downloads.

In February it also instituted ‘Bouncer’, an automated security scanning system designed to weed out malware before it gets near users.  This has had some success but the sheer size and fragmentation of the OS still works against the company is some parts of the world.

It would be a mistake to see Android malware as something only Chinese and Russian users have to worry about. In May, a Latvian company was fined for deceiving users with a 'wrapper' app impersonating Angry Birds. Total number of UK users affected by its SME deception: 1,400 that came to light, possibly that didn't.

The oddity of the mobile malware world revealed by F-Secure is underlined by the fact that the defunct Symbian OS still attracts the interest of malware writers, with a 17 percent rise recorded in new examples hitting its still large but dwindling user base in Q3.