Here’s what happens. Whenever you speak into Apple’s voice activated personal digital assistant, it ships it off to Apple’s data farm for analysis. Apple generates a random numbers to represent the user and it associates the voice files with that number. This number — not your Apple user ID or email address — represents you as far as Siri’s back-end voice analysis system is concerned.
Once the voice recording is six months old, Apple “disassociates” your user number from the clip, deleting the number from the voice file. But it keeps these disassociated files for up to 18 more months for testing and product improvement purposes.
“Apple may keep anonymized Siri data for up to two years,” Muller says “If a user turns Siri off, both identifiers are deleted immediately along with any associated data.”
Also, even if the Siri data is not linked directly to users, people should be careful about what they say to their personal digital assistant. Transcripts “of what you say to Siri could reveal sensitive things about you, your family, or business,” she added. “Siri works for Apple, so make a note to yourself to really think before you speak.”