"This brochure is intended to help contractors within the National Industrial Security Program recognize possible indications of espionage being committed by persons entrusted to protect this nation's secrets. Not every suspicious circumstance or behavior represents a spy in our midst, but every situation needs to be examined to determine whether our nation's secrets are at risk. DSS [Defense Security Service] defines insider threat as: Acts of commission or omission by an insider who intentionally or unintentionally compromises or potentially compromises DoD's ability to accomplish its mission. These acts include, but are not limited to, espionage, unauthorized disclosure of information, and any other activity resulting in the loss or degradation of departmental resources or capabilities."
Defense Security Service: http://www.dss.mil/