FORTUNE - Feb 3 - The number of monthly downloads of Telegram and Signal has skyrocketed since Oct and, in Jan, surpassed Facebook's Messenger. The growth in downloads for Signal has been especially pronounced, shooting from ~1.2M a year ago to ~30M by late January. Messenger and WhatsApp are used by 1.3B and 570M, respectively, compared to 46M daily users for Telegram and 13M for Signal. The reasons for the apps' recent popularity regarding concerns over Facebook's privacy practices.