Apple introduced two the new tracking technologies with iOS 6 — identifierForAdvertising (IDFA) and identifierForVendor (IDFV). These allow something that Apple had previously limited by denying app developers use of a device's UDID; but advertisers can now track and target users of the operating system.
If you don't mind advertising, that's all well and good, but for those of you who don't like being tracked by anyone, turning the feature off is possible — but a little unintuitive. Here's how you can put an end to it.
First, open your iDevice's settings menu. Instead of going to the "Privacy" option, open up the "General" settings. Then, select "About".
From here, scroll down until you see "Advertising".
From here, you'll see that it's set to "off". What's the problem? It's the limitations on ad tracking that are turned off, not the tracking itself. Very sneaky, Apple. In order to stop the tracking, you need to set it to "on".
There you go. Your iPod, iPhone or iPad is now safe from advertiser tracking.