Whatsapp has come under fire in a report by Dutch and Canadian data protection authorities for the way in which it access your entire address book without asking.
The particular contention is that it accesses numbers of contacts who don't use the app themselves. The report states that: "information may only be retained for so long as it is required for the fulfillment of an identified purpose."
For its part, Whatsapp has said that numbers for contacts without the app are encrypted and only stored in case they sign up in the future.
Jacob Kohnstamm, chairman of the Dutch Data Protection Authority, said: "Both users and non-users should have control over their personal data and users must be able to freely decide what contact details they wish to share with WhatsApp."
If you're running Whatsapp on an iOS6 device, then you have the option to select which contacts to upload to Whatsapp, but for iDevices running an older version - or any Android device - the app does this automatically.
The report details the possibility of messages being intercepted or disguised as being from a different user. In response, Whatsapp has said it will strengthen its message encryption and user identification procedure.