Department of Defense Cyber Support to Civil Authorities Act of 2015

Directs the Department of Defense (DOD) to develop a comprehensive plan for the U.S. Cyber Command to support civil authorities in responding to cyber attacks by foreign powers against the United States or a U.S. person.

Requires the plan to include: (1) a plan for internal DOD collective training activities to be integrated with exercises conducted with other federal agencies and state and local governments; (2) any historical frameworks used in the formulation of the plan; (3) descriptions of the roles, responsibilities, and expectations of federal, state, and local authorities, as well as the active and reserve components of the Armed Forces; and (4) any legislative and administrative actions necessary to carry out the plan.

Directs the Government Accountability Office to review such plan.