The site went down Monday afternoon and as of 7 p.m. EST Monday evening, it was still down. Initially, the group had a message pop up on the site saying: "Your commanders admit they are training the people they have sent you to die fighting." The message no longer appears.
Army leaders acknowledged the hack with Army Brig. Gen. Malcolm Frost releasing this statement:
"Today an element of the Army.mil service provider's content was compromised. After this came to our attention, the Army took appropriate preventive measures to ensure there was no breach of Army data by taking down the website temporarily."
Pentagon leaders have said their websites and data servers are under constant attack from various groups. Five months ago, U.S. Central Command's social media accounts were hacked by a group who supported the Islamic State in Iraq and Syria (ISIS).
Last week, the federal government said a group of hackers from China executed one of the largest cyber attacks in U.S. history. The group gained access to data from the Office of Personnel Management -- the human resources department for the federal government -- and the Interior Department.