Melissa, an ex-employee of an organization, was fired because of misuse of resources and security...

 Melissa’s actions classify her as a malicious insider. This category includes individuals who intentionally misuse access to harm the organization. Her intent to seek revenge and her deliberate targeting of the company’s network due to a grudge from being fired are indicative of a malicious insider threat. References: This explanation is based on general cybersecurity knowledge and definitions of insider threats. For specific references, please consult the EC-Council Certified Security Specialist (E|CSS) documents and study materials.