Which insider threat results from a disgruntled employee intentionally damaging the corporate network?

The classification of the insider threat as a "malicious insider" is appropriate because it specifically refers to individuals who intentionally cause harm to an organization's information systems or data. A disgruntled employee, in this context, acts out of personal grievances or dissatisfaction with the company, which motivates them to deliberate harm. This behavior goes beyond errors or negligence—characteristics associated with other types of insiders.

In contrast, a professional insider refers to those who have a level of expertise or a legitimate purpose in their access but may mishandle sensitive information, while a negligent insider involves individuals whose accidental mishandling of data or systems leads to security incidents without intent to harm. An unwitting insider, on the other hand, is typically unaware of their actions leading to security issues. In summary, the term "malicious insider" accurately embodies the intentional and harmful actions of a disgruntled employee toward the corporate network.