-- Changes announced by WhatsApp have drawn the ire of privacy advocates, who say that the messaging service's plan to share user data with parent company Facebook is against the law and should be blocked.
The changes will allow the popular app -- which says it has more than one billion users -- to "coordinate more with Facebook" by sharing the user data, they said. The move prompted The Electronic Privacy Information Center (EPIC) and the Center for Digital Democracy to announce they would be filing a complaint with the Federal Trade Commission (FTC).
WhatsApp says will allow the companies to better fight spam, track basic usage statistics and display more relevant advertisements and friend suggestions to users.
In other words, Facebook would be able to use phonebook data from WhatsApp to help users find friends who they chat with on WhatsApp, but who they have not "friended" on Facebook, a WhatsApp spokesperson told ABC News.
The messaging service insists that the contents of users’ messages, "stay private and no one else can read them. Not WhatsApp, not Facebook, nor anyone else," when they’re encrypted, and maintains that banner advertisements will continue to be barred within its app.
Users can decide to opt-out of the changes, though some time restrictions apply.
However, even the basic sharing of user data has generated controversy.
Facebook acquired the messaging service in 2014 for $22 billion, according to Bloomberg.
At the time the acquisition was announced, a blog post on the WhatsApp website told users, "Here’s what will change for you, our users: nothing," and said "WhatsApp will remain autonomous and operate independently."
The blog post -- from February, 2014 -- does not explicitly rule out data sharing with the parent company.
In a complaint filed with the FTC a few weeks after the acquisition was announced, EPIC said, “WhatsApp built a user base based on its commitment not to collect user data for advertising revenue,” and noting that “Facebook routinely makes use of user information for advertising purposes,” claimed that it intended to use WhatsApp user data for this purpose.
Facebook, like many free online services, uses user data to target advertising at users that is relevant to their interests.
Therefore, EPIC claimed, that the acquisition would "violate WhatsApp users’ understanding of their exposure to online advertising and constitutes an unfair and deceptive trade practice," which it claimed would be in violation of FTC rules.
A few weeks later, in April 2014, the FTC sent a letter to the companies saying that they had made privacy guarantees to users, and that "regardless of the acquisition, WhatsApp must continue to honor these promises to consumers," and "if the acquisition is completed and WhatsApp fails to honor these promises, both companies could be in violation" of the law and an earlier agreement between the FTC and Facebook.
The letter, according to a press release from the FTC, stated that Facebook must "get consumers’ affirmative consent before making changes that override their privacy settings, among other requirements."
The FTC did not immediately respond to ABC News' request for comment. Facebook did not comment separately from WhatsApp