In February last year, soon after the Russia-Ukraine conflict occurred, a user profile matching that of Airman Jack Teixeira began posting secret intelligence on a previously undisclosed chat group on social platform Discord, the newspaper reported, adding the group had about 600 members.

This chat room was publicly listed on a YouTube channel and was easily accessible. The user claimed to be posting information from the National Security Agency, the Central Intelligence Agency and other intelligence agencies, according to the New York Times.

The case is believed to be the most serious US security breach since 2010, when more than 700,000 documents, videos and diplomatic cables were leaked. The Pentagon has called the leak a “deliberate, criminal act.”

The leaks did not come to light until they were reported in early April even though the documents were posted earlier. The Pentagon declined to comment on the new report by the New York Times.