But what about the apps, which provide the functionality of devices? Hundreds of thousands of different apps for mobile devices are available through commercial stores and open source repositories. Billions of copies of these apps have been purchased, and this number is projected to increase dramatically. However, with this growth comes an increase in the spread of potentially dangerous security vulnerabilities. Because of an app's low cost and high proliferation, the threat of these vulnerabilities could be far greater than that of traditional computers.