How should calls to a custom Apex web service be secured for Salesforce to accept only secure connections from the ETL tool?

Two-way SSL (Secure Sockets Layer) is an effective approach to securing calls to a custom Apex web service in Salesforce, particularly when it comes to ensuring that only secure connections from an ETL tool are accepted.

In two-way SSL, both the client and the server authenticate each other. The ETL tool would present a digital certificate to Salesforce during the SSL handshake process. Salesforce also presents its certificate back to the ETL tool, which allows both parties to verify their identities. This mutual authentication enhances the security of the connection by ensuring that both sides are trusted entities.

This method is particularly advantageous because it not only encrypts the data transmitted between the ETL tool and Salesforce but also prevents unauthorized access by ensuring that only clients with valid certificates can connect. This effectively reduces the risk of data interception and man-in-the-middle attacks.

Other security methods like VPN, profile security, and IP whitelisting serve different purposes or might not provide the same level of identity verification as two-way SSL in this scenario. While a VPN can provide a secure tunnel for connections, it does not authenticate the specific client applications requesting access. Profile security relates to user permissions within Salesforce, and IP whitelisting only restricts access based on IP addresses without the necessary