"I'm a pretty paranoid and sophisticated user," says Schmidt, whose firm provides information security and risk management services. "I didn't think I'd be vulnerable to this sort of thing, but because I wasn't familiar with the user interface, I clicked on the ad. It really surprised me."

Fortunately, Schmidt halted the download when he realized what was going on and caught it before anything bad happened to his phone. He's not sure what the malware would have installed on his phone, but he suspects it could have been some kind of spyware, such as a keystroke logger, or some other application that would turn his computer into a spam-mailing bot or otherwise compromise his security and privacy.

Schmidt's experience with mobile malware--specifically, with a mobile --illustrates the challenges users face detecting and preventing mobile malware from infecting their smartphones. It also demonstrates the sophistication and ever-changing nature of security threats targeting mobile devices.

The Mobile Malware Phenomenon: Why It's Hard to Detect

Mobile malware is proliferating at an astonishing rate. Security threats targeting mobile devices between 2010 and 2011, according to research from . In December 2011 alone, Kaspersky identified more new mobile malware apps than it identified between 2004 and 2010.