Chatter on social media about the policy change caused a mini exodus among WhatsApp's two billion users to Signal – a messaging app that most security experts recommend. Signal also provides the end-to-end encryption protocol that WhatsApp uses.
WhatsApp's wording in the notification about its privacy update said users must accept the policy update after February 8 and suggested an alternative was to delete the WhatsApp account. WhatsApp's previous policy let users opt-out of most sharing of user data with Facebook.
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Telegram also claimed to have gained 25 million new users in the past three days, pushing its user numbers beyond 500 million.
Facebook has now explained the policy changes, which take effect on February 8, are actually about WhatsApp users messaging a business on WhatsApp.
"We want to be clear that the policy update does not affect the privacy of your messages with friends or family in any way. Instead, this update includes changes related to messaging a business on WhatsApp, which is optional, and provides further transparency about how we collect and use data," WhatsApp says in the FAQ.
WhatsApp stressed that Facebook can't see private WhatsApp messages and nor can WhatsApp because of end-to-end encryption. Additionally, neither WhatsApp nor Facebook can see users' locations shared with each other. WhatsApp says it doesn't share users' contacts with Facebook or its other apps.
However, the FAQ also explains the three key scenarios where WhatsApp user data and communications can end up on Facebook's servers, but these are limited to communications with businesses via WhatsApp. Those communications can be used to target ads to the user on Facebook.
WhatsApp explains it is "giving businesses the option to use secure hosting services from Facebook to manage WhatsApp chats with their customers, answer questions, and send helpful information like purchase receipts."
"Whether you communicate with a business by phone, email, or WhatsApp, it can see what you're saying and may use that information for its own marketing purposes, which may include advertising on Facebook. To make sure you're informed, we clearly label conversations with businesses that are choosing to use hosting services from Facebook."
Additionally, with Facebook commerce features like Shops, Facebook is allowing businesses to display their goods within WhatsApp. Facebook says that when WhatsApp users choose to use these features, it will inform users within the WhatsApp app how a person's data is being shared with Facebook.
The third way is via ads on Facebook with a button to message a business using WhatsApp.
"If you have WhatsApp installed on your phone, you'll have the option to message that business. Facebook may use the way you interact with these ads to personalize the ads you see on Facebook," said WhatsApp.