It seems more and more apps can listen in on what you’re saying via your iOS device’s built-in microphone. While most of this is probably harmless, if you’re concerned about privacy, you should learn how to control each app’s access to your iOS device’s microphone.
You may notice that any app that wants to access your device’s microphone has to ask first. On the first launch of any new app that will use your microphone, you’ll see a dialog box asking if it’s OK to access it. If you tap “OK,” the app is granted access to your mic from then on. Here’s how to revoke that access if you later decide you don’t want the app listening in.
In iOS 7, go to “Settings” -> “Privacy” -> “Microphone.” Here, you’ll see a list of apps that currently have access to your iOS device’s microphone. Next to each, you’ll see a toggle switch to turn access off and on. If a switch is green, that means it has access. Tap the switch to turn off access to the mic for that app. (The switch will turn white.)
While most apps that ask for access to your iOS device’s microphone have a good reason to need access, at least this way you can see which apps use that access, and turn off that access if desired.