What Is Signal, the App Used to Accidentally Send a Reporter Military Plans?

According to the Atlantic, top White House officials used the end-to-end encrypted messaging app Signal to discuss military strikes in Yemen before those strikes were carried out on March 15. White House National Security Council spokesman Brian Hughes confirmed the messages' authenticity to ABC News, and this revelation has drawn criticism from others in the government. "If true, these actions are a brazen violation of laws and regulations that exist to protect national security, including the safety of Americans serving in harm's way," the top Democrat on the House intelligence committee, Jim Himes, said according to the Guardian. "These individuals know the calamitous risks of transmitting classified information across unclassified systems, and they also know that if a lower-ranking official under their command did what is described here, they would likely lose their clearance and be subject to criminal investigation." But what is Signal, and have government officials used it befo ... Read full article.