The most effective risk mitigation process for the identified vulnerability of "outdated software" is a systematic patch management program, which involves regularly implementing security patches and updates. This directly remediates the vulnerability. For a new core banking system requiring both high security and scalability for a large number of transactions, a hybrid cloud topology is the best approach. It allows the financial institution to host sensitive data and core processing on a highly secure private cloud or on-premise infrastructure while leveraging the scalability and flexibility of a public cloud for less sensitive, customer-facing applications. This model provides an optimal balance of security, compliance, and performance.

A. Public cloud topology is generally not the first choice for a core banking system due to significant security, data sovereignty, and regulatory compliance concerns.

C. Installing antivirus software is a necessary endpoint control but does not directly remediate the specific vulnerabilities of outdated software or weak password policies.

D. Security audits and penetration testing are assessment activities that identify risks; they are not mitigation processes that correct vulnerabilities.

1. NIST Special Publication 800-40 Revision 4 (Draft), Guide to Enterprise Patch Management Planning: Preventive Maintenance for Technology. Section 2.1, "The Importance of Patch Management," states, "Patch management is the process for identifying, acquiring, installing, and verifying patches for products and systems. Patches correct security and functionality problems in software and firmware." This supports implementing patches as a direct mitigation for outdated software.

2. NIST Special Publication 500-292, NIST Cloud Computing Reference Architecture. Section 4.3, "Cloud Deployment Models," describes the hybrid cloud as a composition of two or more distinct cloud infrastructures (private, community, or public). It notes this model allows organizations to "keep the critical applications and data in a traditional data center or private cloud," which is the standard approach for sensitive financial data, while using public cloud resources for other workloads.

3. Carnegie Mellon University, Software Engineering Institute (SEI). (2017). Best Practices for Cloud Security. In discussions of cloud deployment models for regulated industries, the document highlights that a hybrid approach enables organizations to meet stringent security and compliance requirements for core systems while gaining the agility of public cloud services for other business functions. This aligns with the needs of a modern financial institution. (Reference: General principles outlined in SEI publications on cloud adoption and security).