To secure all internal APIs within an integration solution by using an API proxy to apply required authentication and authorization policies, the organization should use API Management (APIM). APIM provides a comprehensive platform to manage, secure, and analyze APIs. It allows the IT team to create API proxies, enforce security policies, control access through authentication and authorization mechanisms, and monitor API usage.

Using APIM for this purpose ensures that internal APIs are protected with standardized security policies, facilitating centralized management and governance of API traffic. This approach is specifically designed for managing APIs and their security, making it the most suitable choice among the options provided.

References

MuleSoft Documentation on API Management

Best Practices for API Security and Governance