As a rule, rogue Android apps don't last long on Google Play -- either Google catches them quickly, or enough people complain that something gets done. That doesn't appear to have happened with a recent batch of apps, though. Antivirus developer Avast has noticed that multiple titles, including some with millions of downloads, have been harboring a sneaky form of adware that tries to fool you into either paying for content or violating your privacy. The apps will often work normally for days, but eventually pester you with ads warning about non-existent updates and viruses every time you unlock your phone. If you're tempted enough to tap one of the ads, you're steered to far more dangerous content that may send premium text messages (without asking, naturally), harvest personal info or otherwise compromise your device.