What's a cyber-criminal to do? First, the general public is replacing the loop-hole ridden Windows XP on their PCs in favor of the more secure Windows 7 operating system, which is frustrating enough, but now, increasingly, a large percentage of computing isn't being done on PCs at all.

So where do you go with your particularly juicy bit of malware or spyware, or to steal a few identities? To the smartphones, of course.

With smartphones outselling PCs for the first time — 421 million of the hand-held computers are expected to be sold worldwide this year, according to market analysts at IDC — the long-predicted crime wave on hand-held devices appears to have arrived, according to an article by Riva Richmond that appears today in the New York Times. According to the mobile security firm Lookout, malware and spyware appeared on nine out of 100 phones it scanned in May, more than twice the rate in December 2009.

So how to keep your smartphone from turning into a little hand-held window into your personal identity for any hacker who cares to look in? The trick, writes Richmond, is to start thinking of your smartphone as a PC.

While most unwelcome invaders on smartphones require the user to accept or install a program that arrives via text message (and according to Finish security firm F-Secure there are now more than 500 varieties of these), experts warn that automated attacks are possible and could emerge in the future...the very near future.

So who is most vulnerable? If you live in China or Eastern Europe and have a phone that runs Nokia's Symbian mobile operating system, you are most vulnerable. According to F-Secure, a full 88 percent of mobile phone-based scams target Symbian. Though Symbian is currently the most commonly used smartphone platform in the world, the company recently announced it would be ditching the OS in favor of Microsoft’s Windows Phone operating system, which is thought to be more secure.

Confident you're safe that since you're not living in China or Eastern Europe and have a phone that doesn't run Symbian? Don't be. Criminals have attacked phones running Google’s Android, Research In Motion’s BlackBerry, Apple’s iPhone and Microsoft’s Windows Mobile operating system software, according to the Times.

And experts warn that more is to come.