What is ‘classified’ information? What are ‘secure’ communications? Here’s a primer

WASHINGTON — The Trump administration’s use of a popular messaging app to discuss sensitive military plans — with a journalist on the text chain — is raising questions about security and the importance of safeguarding the nation’s secrets. It’s also highlighting the differences between classified and public information, and demonstrating that even encrypted apps like Signal can lead to embarrassing leaks if the humans doing the texting don’t follow basic security tips. President Donald Trump’s administration says no classified material was leaked when senior officials used Signal to discuss upcoming attack plans against the Houthi rebels in Yemen — even though a journalist was on the chat. Material categorized as “controlled unclassified information,” while not secret, is still considered sensitive enough that military service members are prohibited from discussing it on unsecured devices like personal phones. The Pentagon hasn’t said whether Hegseth declassified the attack plans before or after the Signal conversation, but Ratcliffe, Gabbard and the White House have all said the chats contained no classified information.