The number of new users installing messaging app Signal every day is on track to cross 1 million, putting it closer to levels seen by larger rival WhatsApp, following an update to the Facebook Inc-owned (FB.O) app's privacy policy.

About 810,000 users globally installed Signal on Sunday, nearly 18-fold compared with the download numbers on Jan. 6, the day WhatsApp updated its privacy terms, according to data from research firm Apptopia.

WhatsApp's new privacy terms reserve the right to share user data, including location and phone number, with its parent Facebook Inc (FB.O) and units such as Instagram and Messenger.

Privacy advocates have questioned the move citing Facebook's track record in handling user data, with many suggesting users to migrate to platforms such as Telegram and Signal.

To cope with the number of new users, Signal said on Sunday it had added more servers to handle the traffic. Up until recently, the non-profit app was largely used by journalists and human rights activists looking for a more secure and encrypted mode of communication.

WhatsApp, which saw a 7% decline in daily installs on Sunday compared with Wednesday, was downloaded by nearly 1.2 million users on Jan. 10, according to Apptopia.