As consumers grow concerned about hacking and government surveillance, more of them are turning to secure apps to send messages free of prying eyes.
On Monday, the analytics firm Apptopia published some numbers that show the growing popularity of these apps, including which ones consumers are turning to most.
As you can see below, the most downloaded app in 2016 was Telegram, which is a popular communications tool for dissidents (and also for terrorists). It accounted for about 87 % of downloads worldwide, followed by Signal and Wickr, which each accounted for about 6%.
While Telegram is clearly dominant when it comes to downloads, that is not necessarily the most important metric when it comes to evaluating popularity. Instead, the more useful figure may be so-called MAUs, which stands for "monthly active users."
And when it comes to MAUs, Signal has been ascendant in recent months, and may soon rival Telegram. Here are the MAU figures for December 2016 (note they count only iOS users):
Another important finding from the Apptopia data is a recent spike in both downloads and MAUs for Signal: the 410,000 figure seen above represents a nearly four-fold increase from October. This validates a claim by Signal founder, Moxie Marlingspike, that the app soared in popularity after the U.S. election—likely reflecting concerns about surveillance practices under President Trump.
Get Data Sheet, Fortune’s technology newsletter.
Finally, it should be noted that the likes of Signal and Telegram are hardly the only ways for users to send secure messages. The popular app WhatsApp, which is owned by Facebook (fb), also offers end-to-end encryption powered by the same technology that protects Signal. According to Apptopia, WhatsApp downloads dwarfed all the other apps—it was downloaded around 225 million in 2016.
As for the popularly of the secure messaging apps, Apptopia CEO Eliran Sapir explains it this way:
There's always a market for privacy. We started seeing this in 2016 with a series of apps focused on encrypted messaging. As apps are getting slammed for encryption flaws, we are watching this exciting market with curiosity to see if a new player will gain market share because they are the ones who get it right. Remembering that Facebook acquired WhatsApp, we wonder if WhatsApp could find themselves the acquirer.
The "other" category listed above comprises an app called Dust and one called Silent Phone.