It is important to protect yourself and the information that you keep in your phone. iOS 6 allows you to control which apps have access to your contacts list. Follow the steps below to secure your contacts list quickly and easily. If you want to simply delete unwanted contacts see here.
There you go! You can now choose which apps you are comfortable with having access to your contacts and which apps you are not. Just follow these same steps anytime you want to manage any new apps.