When you have a page for an app loaded, there’s that word, permissions, near the top. When click/tap it, you’ll see a list of powers the app will have if you install it. Freeware is the most notorious for overreaching. For instance, and I just picked this as a random free game:
Sudoku Free “requires these permissions:
Network communication -- full Internet access, view network state
Storage -- modify/delete SD card contents
Phone calls -- read phone state and identity
System tools -- prevent phone from sleeping”
Sudoku is just a form of solitaire -- why on earth would it need full Internet access? So it can throw advertisements at you -- that’s how free apps are profitable for the developer. The ads are sometimes very annoying, other times very ignorable. Usually if you plunk down for its paid version, the ads go away.
AppBrain Ad Detector and
Lookout Ad Network Detector are handy apps for keeping an eye on ads. I have eighty-five apps, plenty with banner ads, but I’ve weaned out all the ones with bad stuff, like throwing things on your desktop or notification bar.
Finally, here’s a wonderful dossier on security:
Android permissions explained, security tips, and avoiding malware