One of the Pentagon’s key missions is to lend a hand—or a drone—during natural disasters or other domestic emergencies. But it is unclear, in the event of of a massive data breach, which element of the Defense Department is in charge of military support, according to Congress' watchdog agency.

In other words: When there is an Ebola virus epidemic, for example, the assistant secretary of defense for health affairs steps in to help the civilian government. But it's not clear what military official should organize forces when there is, for instance, a hospital computer virus unleashed by Iran.

U.S. Northern Command says it is the main Pentagon support arm that fends off foreign hackers in the United States, a position at odds with policies and some top brass who say Cyber Command plays the lead in addressing stateside cyberthreats from abroad when asked.

Joseph W. Kirschbaum, Government Accountability Office director for defense capabilities and management, warned that until the Pentagon "clarifies the roles and responsibilities of its components," the military "may not be positioned to effectively employ its forces and capabilities to support civil authorities in a cyberincident."

See also: US Still Doesn’t Know Who’s In Charge of What If Massive Cyber Attack Strikes Nation

In recent years, CYBERCOM and National Security Agency resources have been deployed to deal with privacy breaches at the Office of Personnel Management perpetrated by Chinese hackers, as well as a destructive attack against Sony Pictures Entertainment allegedly orchestrated by North Korea.

"DOD officials stated that the department had not yet determined the approach it would take to support a civil authority in a cyberincident and, as of January 2016, DOD had not begun efforts to issue or update guidance and did not have an estimate on when the guidance will be finalized," Kirschbaum said.

The Pentagon is required by law to develop a plan by next month for CYBERCOM to support civil authorities in the event of a nation-state cyber strike.

But a NORTHCOM concept plan, which is already Defense secretary-approved, states its commander would coordinate a civilian mission that "may include cyber domain incidents or activities — with other DOD components supporting in conducting the missions," Kirschbaum said in an audit made public Monday.

At the same time, other guidance directs Cyber Command to be responsible for supporting civil authorities during a cyberincident, the report noted.

Specifically, Robert Salesses, a deputy assistant secretary for homeland defense integration, testified in June 2015 CYBERCOM would oversee cyberincident troubleshooting. Likewise, a 2010 formal agreement between DOD and Homeland Security Department names CYBERCOM as the Pentagon component that would respond to a civilian network disaster.

For its part, Cyber Command says the Defense secretary likely would call on CYBERCOM, not NORTHCOM, to provide help during a civilian cyber emergency.

Northern Command told a different story. As of September 2015, NORTHCOM officials said "their command had not delegated this responsibility to another command."

Meanwhile, Pacific Command officials told GAO it would take center stage responding to a cyberincident within its area of responsibility with CYBERCOM playing a supporting role, Kirschbaum said.

The reasons for the discrepancies in roles and duties are due to the recent emergence of the cyberthreat, according to the report.

NORTHCOM officials said Defense so far has never received a request for assistance from DHS or any lead federal agency for military support, under a civil authority, for a cyberincident. An official within the office of the deputy assistant secretary for cyber policy said the military "expects to receive more requests to support civil authorities in cyberincidents and acknowledged the need to clarify roles and responsibilities in advance of any requests given the growing focus on cybersecurity," the audit states.

In reaction to a draft audit, the Pentagon on March 14 said it will spell out the officials and components that will aid, as needed, in the event of a U.S. cyber episode.

Defense will release or update guidelines "that clarify DOD roles and responsibilities regarding civil support for domestic cyberincidents," said a response sent by Aaron Hughes, deputy assistant secretary for cyber policy.