As a general rule, it’s a bad idea to buy third-party anti-virus software. That’s doubly true for mobile anti-virus software; generally, the best way to protect yourself is to use common sense. That was rather dramatically demonstrated by… uh, anti-virus software that turned out to be a ridiculous ripoff.
The app, called “Virus Shield”, purported to protect your phone at the tap of the screen. As you may have guessed, it didn’t quite work as advertised, according to CNET:
In fact, it didn’t work at all. After examining the app’s Java code, the app only does one thing. The image changes when you tap the screen, turning the X into a tick. That’s it.
If you’re wondering how the developer got away with this, at $4 a pop, it’s because the app is utterly harmless. Google only scans apps for malware, but it doesn’t check to see if they work as advertised. So, essentially, Google didn’t see anything wrong with the app, because it doesn’t hurt your phone. It just also happens to be a $4 button that doesn’t actually do what it claims to do.
There’s nothing on mobile that’s entirely without risk. Even legitimate apps can be shockingly intrusive. Essentially, before buying anything, look into the developer separately from the Google Play store. See if they’ve got a blog. See what other apps they’ve done. And, of course, always be skeptical of something that sounds too good to be true.