If you search using Siri, that search query could be kept for a very long time. In the Siri’s Privacy agreement, Apple says that it deletes your user data as well as the recent things that you’ve said to Siri whenever you slide the Siri switch off. But it keeps the older stuff.

“If you turn off Siri, Apple will delete your User Data, as well as your recent voice input data,” Apple’s privacy statement reads. “Older voice input data that has been disassociated from you may be retained for a period of time to generally improve Siri and other Apple products and services.”

So what exactly does ‘disassociated’ mean. And ‘period of time’. And using it to ‘generally improve Siri and other Apple products and services’. This is actually fairly open ended.

This matters, because we often say to Siri more personal stuff than we do with search with Google or Bing. Siri is, after all, a personal digital assistant; someone you can dictate messages to. And if that information is stored on Apple’s networks, it could be used by marketers, or by government investigators, or even subpoenaed in a civil suit years later. I promise I am not being paranoid.

In fact Siri was a big enough concern that last year IBM CIO Jeanette Horan, banned Siri outright on IBM’s networks, worrying that what people said to Siri might be stored somewhere.

Despite Apple’s privacy agreement, it is still not crystal clear about its data retention policies. It is not, for example, linked on Apple’s Siri FAQ page. In fact, it doesn’t appear to exist anywhere on Apple’s website.

Apple is not alone. Google, which offers its own Voice Search software on Android phones, says that it anonymizes audio samples and then stores them for up to 24 months to improve its speech recognition software.

So next time you speak to Siri, just be careful.