Social media accounts for the U.S. military’s Central Command appeared to have been hacked on Monday, with the command posting threatening messages on Twitter and YouTube to American troops. In a statement, the Central Command confirmed that its Twitter account had been “compromised” and said it “is taking appropriate measures to address the matter.” The statement did not elaborate on the extent or seriousness of the hack or who may have been responsible. The account was disabled by Twitter around 1:10 p.m. White House Press Secretary Josh Earnest said the Obama administration is “examining and investigating the extent of the...