A man is seen as a silhouette as he checks a mobile device whilst standing against an illuminated wall bearing Telegram's logo in this arranged photograph in London, U.K., on Tuesday, Jan. 5, 2016. The Telegram messaging app, which allows users to encrypt text that self-destructs on a timer, took down a number of channels Islamic State was using for propaganda, highlighting the actions some online companies are taking to react to terrorism. Photographer: Chris Ratcliffe/Bloomberg via Getty Images