Android is one of the most targeted mobile platforms, one reason is that it has a big part of the smartphone market. One of the features widely attacked by malware is the Android mechanism to grant permissions to applications. Applications announce their lists of required permissions in their installation packages, and users decide whether to grant those permissions or not. However, most users do not understand the meaning of such permissions. This work proposes the use of categories to help users make a decision; a category represents an application's purpose. It is easy for users to map an application to a category because category names are meaningful. Once a user establishes a mapping application-category, it is possible to automatically evaluate if the permissions an application requests are valid.