An unintentional insider threat is (1) a current or former employee, contractor, or business partner (2) who has or had authorized access to an organization’s network system, or data and who, (3) through action or inaction without malicious intent, (4) unwittingly causes harm or substantially increases the probability of future serious harm to the confidentiality, integrity, or availability.

–Unintentional Insider Threat and Social Engineering, Insider Threat Blog, Carnegie Mellon University (CMU) Security Engineering Institute (SEI), by David Mundie, 03/31/2014