Last summer, Apple stopped allowing app makers to use a unique identifier embedded in iPhones and iPads to track users as they move from app to app, which is an important way for advertisers to position their ads for appropriate audiences. A recent Wall Street Journal article explains that the “two high-profile methods now being used by advertisers are the open-source OpenUDID, which uses the phone’s copy-and-paste function to track, and Open Device Identification Number (ODIN), which piggybacks off a device’s Media Access Control address (MAC) to track users.” While advertisers claim that such practices are anonymous, but others disagree, stating that even anonymous data can lead to uncovering a user’s identification.