I review a lot of Android apps: Many of them are junk, some are so-so, and a small number are great, providing functionality that should be included in every Android phone or Android tablet. DroidWall (for rooted devices only) is among the elite few. Why? Because DroidWall allows you to specify which apps can access the internet - giving you more control over your phone and enabling you to protect yourself against unauthorized data connections.
Unfortunately, many apps misuse their permissions in order to upload your contacts list without asking, report your physical location to third-party advertisers, or abet other invasions of privacy. DroidWall puts the power back into your hands. The app's simple dashboard controls how your installed apps can access the Internet. Each app is listed with two checkboxes: One is for Wi-Fi data access (useful for keeping apps that use a lot of data from eating up your cellular data), and the other is for cellular data. Check the box to allow access; leave it blank to deny access. When you're done, activate the firewall.
Of course, many apps (for example, your Web browser) have legitimate reasons to access the Internet. Blocking these apps may cause them to behave erratically or may prevent them from working altogether. If an app doesn't have any obvious legitimate reason to connect to the Internet, however, you can probably block it without adverse effects. If you do experience problems, you can always go back into DroidWall and re-enable an app's network connection if you must--or turn off the firewall entirely if you don't plan on using it.
It's worth noting that many free apps rely on in-app advertising for revenue. In such cases, the app may try to connect to the Internet in order to serve up advertisements. Using DroidWall to block the app will block the ads--but it will also block the app developer's revenue stream. On the other hand, many advertisers track your location and other information, and DroidWall can put a stop to that unwelcome behaviour. Check out PC Advisor's Best Android Apps page for more advice.