“To help identify and prevent fraud, information about how you use your device, including the approximate number of phone calls or emails you send and receive, will be used to compute a device trust score when you attempt a purchase. The submissions are designed so Apple cannot learn the real values on your device. The scores are stored for a fixed time on our servers.”
This is likely to alarm many users, but Apple has promised that it is not tracking users and believes that privacy is a fundamental human right and they believe in being transparent about what kind of data they collect. Apple also doesn’t see the contents of the message just how many phone calls and emails the user is receiving. At this time, it is not possible to see your trust score.
It isn’t known how tracking the number of phone calls and emails can prevent fraud but at least Apple has told users that this information is not being used for targeted advertising and just for fraud prevention.