Apple keeps your Siri data in its servers for up to two years, it has been revealed.

Apple spokesperson Trudy Muller told Wired that the company only collects Siri voice clips, which can include questions, messages and other commands, in order to improve the voice-activated personal assistant that was launched with the iPhone 4S in 2011. "Our customers' privacy is very important to us," she said, adding that Apple takes steps to ensure that the data is kept anonymous.

Wired explains that, when a user speaks to Siri, the voice-clip gets sent to Apple's data farm for analysis. Apple creates a random string of numbers to represent the user, therefore keeping their identity anonymous. Each time that user speaks to Siri, the same string of numbers (which is not an Apple ID or email address) will be associated to the voice clips collected.

After six months, Apple "disassociates" the number from the voice recording, but can keep the file for up to 18 more months in order to carry out further testing and help improve Siri, Muller said.

 

"Apple may keep anonymised Siri data for up to two years," Muller added. "If a user turns Siri off, both identifiers are deleted immediately along with any associated data."

You can turn Siri off on your supported iOS device by going to Settings > General > Siri.

While its understandable that Apple would want to keep Siri data in order to improve the service, American Civil Liberties Union lawyer Nicole Ozer says that Apple should make it clear to users that this is the case in its Siri FAQ, with a link to the Siri Privacy policy. At present, users can only find the Siri Privacy policy within the settings of an iPad or iPhone, so they aren't made aware of Apple's storage of voice clips until after purchasing an iOS device.

"There is no good reason for Apple not to include information about privacy practices on their Siri FAQ page," Ozer told Wired, adding that, while data is anonymous, "what you say to Siri could reveal sensitive things about you, your family, or business."

Gigaom's Erica Ogg highlights that Apple's two years of data storage is longer than Yahoo, Microsoft and Google's, all of which retain search data for 18 months.

How do you feel about Apple's storage of Siri data? Let us know in the comments section below, or on Twitter.

See also:

Amazon has reportedly acquired Siri rival Evi for Kindle Fire, hints at future smartphone

Inside Siri's brain: The challenges of extending Apple's virtual assistant

Apple increasing Siri resources with recruitment drive

Apple accused of stealing Siri from Chinese firm