What is a proper method to protect web service call credentials included in a managed package?

Utilizing named credentials to maintain the security of credentials is the best practice for protecting web service call credentials within a managed package. Named credentials provide a centralized and secure way to define authentication for an external service. By using named credentials, you can store the endpoint URL and the authentication parameters securely without exposing sensitive information in your code.

This method encapsulates the authentication logic and reduces the risk of credential leakage, as they are stored securely within the platform. When employing named credentials, access control can be easily managed, and they can take advantage of the platform's built-in secure storage mechanisms, such as encrypted fields and OAuth for improved security. Additionally, named credentials can simplify maintenance and reduce the risk of errors when making API calls, isolating authentication details from the business logic and providing a clear separation of concerns.

Although using protected custom settings and custom objects with encrypted fields can also provide a layer of security, named credentials are specifically designed for handling such scenarios in a more streamlined fashion, ensuring the credentials are managed and utilized within best security practices.