Which standard focuses specifically on securing SOAP messages?

The standard that focuses specifically on securing SOAP messages is Web Services Security (WSS). WSS provides a framework that ensures the integrity, confidentiality, and authentication of SOAP messages exchanged over networks. This standard is particularly important in service-oriented architectures where SOAP is commonly used for web services.

WSS allows security to be embedded directly into the SOAP messages by defining a set of rules and protocols. It supports various security mechanisms, such as encryption and digital signatures, which are vital for protecting sensitive data transmitted in SOAP messages.

The other options mentioned do not specifically address the security of SOAP messages. ISO/IEC 27034 is a standard for application security and does not target SOAP specifically. The Ex-Frame-Options Header is a security measure related to preventing clickjacking attacks, and it does not pertain to SOAP messages. Lastly, The OWASP Secure Headers Project focuses on defining and implementing HTTP security headers to protect web applications but does not address SOAP messaging directly. Hence, the choice of WSS as the correct answer is based on its focused purpose and appropriateness in securing SOAP messages specifically.