What type of security incident involves an attacker disseminating malware on organizational systems?

The situation described pertains to the act of an attacker disseminating malware within organizational systems, which is fundamentally an issue of unauthorized access by malicious means. When malware is introduced, it typically results from an unauthorized entity exploiting vulnerabilities within the system, which aligns closely with unauthorized access incidents. This type of incident encompasses a range of activities where attackers gain access to systems for harmful purposes, including deploying malware that can compromise system integrity, steal data, or disrupt services.

In contrast, inappropriate usage incidents usually involve employees misusing organizational resources but do not necessarily involve malicious intent or malware dissemination. Data breach incidents refer to unauthorized access to sensitive data, often with the intent to steal or leak that information, while malicious insider incidents focus on actions taken by individuals within the organization who have legitimate access but use it to conduct harmful activities. These distinctions highlight why the primary classification of the incident described is aligned with unauthorized access incidents involving malware.