DOD networks are highly susceptible to attack. Military cyber professionals are trained to defend the network.

Army Maj. Peter Semanoff pins a Bronze Star medal onto the lapel of World War II veteran Clarence Smoyer, Sept. 18, 2019, at the National World War II Memorial in Washington.

Veterans Clarence Smoyer and Joe Caserta stand near a Pershing tank, similar to the ones they were both crewmembers of during World War II, Sept. 18, 2019, near the National World War II Memorial in Washington. Both men were present in their respective tanks in Cologne, Germany, March 6, 1945, when Smoyer's tank crew "Eagle 7," took out a German tank.

The unauthorized removal of classified information from the workplace is one action of an insider threat. A "secret" cover sheet typically designates a folder that contains classified material that can be viewed only by those with proper clearance. This folder contains no classified material, however, and the cover sheet itself is unclassified.

Drinking too much or drinking on the job are not necessarily insider threats. But they are indicators that an employee could evolve into an insider threat.

Image memes such as this one ask users to construct and share on their social media feeds new, "fun" information that is constructed from their personal information.

A common access card, or CAC, is commonly used by security-cleared personnel to access classified systems.

DOD networks are highly susceptible to attack. Military cyber professionals are trained to defend the network.

DOD networks are highly susceptible to attack. Military cyber professionals are trained to defend the network.

A "secret" cover sheet typically designates a folder that contains classified material that can be viewed only by those with proper clearance. This folder contains no classified material, however, and the cover sheet itself is unclassified.

A common access card, or CAC, is commonly used by security-cleared personnel to access classified systems.

To gain a security clearance, potential employees spend a significant amount of time gathering personal information and entering it into an online web-based system.

Joy Brinduse and her brother, Peter Lautzenheiser, attend a ceremony in the Pentagon courtyard marking the founding of the National League of POW/MIA Families, June 21, 2019.

Kelly McKeague, director of the Defense POW/MIA Accounting Agency, speaks at a ceremony in the Pentagon courtyard marking the founding of the National League of POW/MIA Families, June 21, 2019.

David L. Norquist, who is performing the duties of the deputy secretary of defense, greets Ann Mills-Griffiths, chairman of the board of the National League of POW/MIA Families, during a ceremony in the Pentagon courtyard marking the founding of the National League of POW/MIA Families, June 21, 2019.

David L. Norquist, who is performing the duties of the deputy secretary of defense, greets Joy Brinduse, during a ceremony in the Pentagon courtyard of the founding of the National League of POW/MIA Families, June 21, 2019.

Jonathan Rath Hoffman, assistant to the secretary of defense for public affairs, speaks at the National World War II Memorial in Washington during an event commemorating the 75th anniversary of D-Day invasion, June 5, 2019. Volunteers read the names of nearly 9,000 American service members who were killed in France during Operation Overlord, which began June 6, 1944.

During a June 5, 2019, commemoration event at the National World War II Memorial, volunteers read the names of nearly 9,000 American service members who were killed in France during Operation Overlord, which began June 6, 1944.

During a June 5, 2019, commemoration event at the National World War II Memorial, volunteers read the names of nearly 9,000 American service members who were killed in France during Operation Overlord, which began June 6, 1944.

During a June 5, 2019, commemoration event at the National World War II Memorial, volunteers read the names of nearly 9,000 American service members who were killed in France during Operation Overlord, which began June 6, 1944.

During a June 5, 2019, commemoration event at the National World War II Memorial, volunteers read the names of nearly 9,000 American service members who were killed in France during Operation Overlord, which began June 6, 1944.

During a June 5, 2019, commemoration event at the National World War II Memorial, volunteers read the names of nearly 9,000 American service members who were killed in France during Operation Overlord, which began June 6, 1944.

A joint service color guard presents the colors during an event at the National World War II Memorial, June 5, 2019. Volunteers read the names of nearly 9,000 American service members who were killed in France during Operation Overlord, which began June 6, 1944.

Gunnery Sgt. Robert Singer of the "President's Own" U.S. Marine Corps Band plays taps at the National World War II Memorial in Washington during an event commemorating the 75th anniversary of the D-Day invasion, June 5, 2019. Volunteers read the names of nearly 9,000 American service members who were killed in France during Operation Overlord, which began June 6, 1944.

Flags on display at the National World War II Memorial in Washington during an event commemorating the 75th anniversary of the D-Day invasion, June 5, 2019. Volunteers read the names of nearly 9,000 American service members who were killed in France during Operation Overlord, which began June 6, 1944.

Brookings Institution Senior Fellow Michael O'Hanlon speaks with Army Lt. Gen. Charles Hooper, director of the Defense Security Cooperation Agency, during a discussion at the Brookings Institution in Washington, June 4, 2019.

Dana Deasy, chief information officer for the Defense Department, makes an official entrance with his wife and Marine Corps. Lt. Gen. Loretta E. Reynolds, deputy Marine Corps commandant for information, at the evening parade at Marine Barracks Washington, May 31, 2019.

Vice Chairman of the Joint Chiefs of Staff Air Force Gen. Paul J. Selva, Holly Vega, Marine Corps Lt. Col. Javier Vega, and retired Air Force Lt. Gen. Stanley Clarke III, chairman of the Armed Forces Insurance board of directors, participate in the 2019 Armed Forces Insurance Military Spouse of the Year award ceremony at Joint Base Myer-Henderson Hall, Va., May 9, 2019. Selva and Clarke presented Holly Vega with the award for 2019 Armed Forces Insurance Military Spouse of the Year. She was the Marine Corps nominee for the DOD-wide award.

Army Chief of Staff Gen. Mark A. Milley, left, Maria Reed, Army Sgt. 1st Class Patrick Reed and Hollyanne Milley participate in the 2019 Armed Forces Insurance Military Spouse of the Year award ceremony at Joint Base Myer-Henderson Hall, Va., May 9, 2019. Hollyanne Milley introduced Maria Reed as the Army nominee for the DOD-wide award.

Michelle D. Norman and Vice Adm. P. Carter Howe, associate director for military affairs at the Central Intelligence Agency, participate in the 2019 Armed Forces Insurance Military Spouse of the Year award ceremony at Joint Base Myer-Henderson Hall, Va., May 9, 2019. Howe introduced Norman as the Navy nominee for the DOD-wide award.

Albert Frosch, Katelyn Tinsley, Air Force Tech. Sgt. Mark Tinsley, and Lt. Gen. Jacqueline VanOvost, director of the Air Force Staff, participate in the 2019 Armed Forces Insurance Military Spouse of the Year award ceremony at Joint Base Myer-Henderson Hall, Va., May 9, 2019. VanOvost introduced Katelyn Tinsley as the Air Force nominee for the DOD-wide award. Frosch is Van Ovost's spouse.

Vice Commandant of the Coast Guard Adm. Charlie Ray, left, Jessica Manfre, Coast Guard Senior Chief Petty Officer Scott Manfre, and Donna Ray participate in the 2019 Armed Forces Insurance Military Spouse of the Year award ceremony at Joint Base Myer-Henderson Hall, Va., May 9, 2019. Donna Ray introduced Jessica Manfre as the Coast Guard nominee for the DOD-wide award.

Air Force Gen. Joseph L. Lengyel, chief of the National Guard Bureau; Samantha Gomolka; Army Warrant Officer 2 Michael Gomolka; and Sally Lengyel participate in the 2019 Armed Forces Insurance Military Spouse of the Year award ceremony at Joint Base Myer-Henderson Hall, Va., May 9, 2019. Sally Lengyel introduced Samantha Gomolka as the National Guard nominee for the DOD-wide award.

The newly-developed "Airborne Surface Quad Thruster Underwater Interface Device," or ASQUID, grips on to the MK-18 and is lowered via tether from a hovering MH-60S Seahawk helicopter.

Coast Guard Lt. Cmdr. Megan Drewniak, Navy Lt. Bradley Lentz and Air Force Capt. Patrick Lin served as mentors during the 2019 U.S. Senate Youth Program, which ran March 3-8, 2019, in Washington.

Shannon Ryu, a senior at Seoul American Middle High School, a Department of Defense Education Activity school in Seoul, South Korea, and Daniel Posthumus, a junior at Nile C. Kinnick High School, a DODEA school in Yokosuka, Japan, participated in the 2019 U.S. Senate Youth Program in Washington. The program ran March 3-8, 2019, and included 104 students.

Coast Guard Lt. Cmdr. Megan Drewniak, Navy Lt. Bradley Lentz and Air Force Capt. Patrick Lin served as mentors during the 2019 U.S. Senate Youth Program, which ran March 3-8, 2019, in Washington.

Shannon Ryu, a senior at Seoul American Middle High School, a Department of Defense Education Activity school in Seoul, South Korea, and Daniel Posthumus, a junior at Nile C. Kinnick High School, a DODEA school in Yokosuka, Japan, participated in the 2019 U.S. Senate Youth Program in Washington. The program ran March 3-8, 2019, and included 104 students.