Defense Secretary Ash Carter on Monday said that the names, photos, and addresses of 100 U.S. military service members purportedly hacked by ISIS supporters and leaked online were not stolen from confidential files.
A post published on the upload website Just Paste It by a group calling itself the "Islamic State Hacking Division" purported to leak "classified information" on 100 military personnel and called for their deaths.
"The Islamic State Hacking Division has hacked several military servers, databases, and emails," the post reads, "and with all this access we have successfully obtained personal information related to military personnel.
"With the huge amount of data we have from various different servers and databases, we have decided to leak 100 addressed so that our brothers residing in America can deal with you."
The group urged sympathizers to launch attacks on the named individuals.
"Kill them in their own lands, behead them in their own homes, stab them to death as they walk their streets thinking that they are safe," the posting said.
But Secretary Carter said Monday that the information was not obtained from confidential government files, the Associated Press reported.
"The information that was posted by ISIL was information taken from social websites and publicly available," Carter said, using an alternative acronym for ISIS. "It wasn't stolen from any [Defense Department] websites or any confidential databases."
However, Carter said the Pentagon was still taking the matter seriously.
A U.S. Marine Corps spokesperson told BuzzFeed News on Sunday that the Naval Criminal Investigative Service had notified all the affected personnel of the "presently unverified threat."
"Vigilance and force protection considerations remain a priority for commanders and their personnel worldwide," Major Paul Greenberg said. "It is recommended Marines and family members check their online/social footprint, ensuring privacy settings are adjusted to limit the amount of available personal information."
A Pentagon spokesperson had told BuzzFeed News on March 21 that officials were investigating the authenticity of the information.
"I can't confirm the validity of the information, but we are looking into it," the spokesperson said. "The safety of our service members is always a concern."
In January, the U.S. Military Central Command's social media accounts were hacked by purported ISIS supporters who called themselves "Cyber Caliphate."
FBI agents said their initial investigations showed no classified material was shared from the accounts, labeling the incident an act of "cybervandalism."
In February, the Twitter account for Newsweek magazine was also hacked by users who stated they were publishing "confidential documents from the U.S. National Cybersecurity Center," before posting images purportedly from the Defense Cyber Investigations Training Academy.