Who implements and operates DoD Information Systems within their specific environment or network?

The role that implements and operates DoD Information Systems within their specific environment or network is the Information Assurance Officer (IAO). The IAO is responsible for ensuring that information systems are operated safely, securely, and effectively according to established policies and procedures. This position involves managing the security posture of the system, conducting assessments, and implementing controls to protect the system from vulnerabilities and threats.

The IAO ensures that the systems meet compliance requirements and provides oversight to implement security measures that align with the Department of Defense's guidelines. This includes configuring systems properly, monitoring for security breaches, and maintaining documentation related to the system's security.

While other roles mentioned have specific functions, such as overseeing access management or investigating malware, they do not primarily focus on the implementation and operational aspects of the systems as the IAO does. This makes the IAO the correct answer in the context of operating and managing DoD Information Systems.