A few days ago I read an article how iOS app developers can uniquely identify my iOS device using its UDID. The thought of various apps being able to track me (with an ID attached) is somewhat unnerving. Also, I do not feel that I am getting a service of higher quality in exchange for letting developers learn about my preferences and habits. While Apple is apparently moving towards deprecating UDIDs, it will take time. Thus, my question: can I somehow restrict access to my device's UDID?
In a word, no, it's currently available for any App to read, and then subsequently use as it sees fit. However, Apple recently made clear that they would not approve future Apps that request it, and so it's use will be negated over time, but of course this won't necessarily apply to the millions of apps already approved.
It's possible to spoof your UDID but only if your iDevice is jailbroken. You can freely try PMP - Protect My Privacy app from Cydia store which helps securing your UDID, Contacts and Location info by shuffling and generating random data access.
Nowdays access to the UUID has been replaced by the Advertising Identifier that you could control if your want to share it with apps. Go to the Privacy section in settings and flip the switch to disable it.
It says "Limit Ad tracker". You can chose it to be on or off. So in other words it will always be ON. That's how I understand it.