The number of botnet infected Google Android devices has rocketed in recent months according to security research.

Botnet hunting firm Damballa said in 2011 half-year report that 40,000 Android devices in the US were under the control of botnet command and control servers.
Some 20,000 devices were under control of botnets by March. That number fell after Google deployed a remote kill function to remove malicious applications from Androids, the report stated.
It then peaked in early July to almost 40,000.
“This peak of around 40,000 is unlikely to be the peak for the year,” Damballa research vice president Gunter Ollmann said. “We expect this upward trend in victim devices to continue.”
He said the number was “almost insignificant” compared to the size of PC-based botnets, which can contain millions of machines.
Historically, mobile malware was limited to SMS fraud and other tactics that did not require a C&C infrastructure. But that is changing as adversaries look to more sophisticated and money-making attacks on mobile devices.
Crime isn't exclusive to the Android platform, Ollmann said. Windows Mobile, Symbian, HP, as well as Apple's iPhone, are being similarly targeted by criminals.