System hardening should include all of the following EXCEPT:

System hardening is a critical process that aims to reduce vulnerabilities and improve the security posture of IT systems. It involves applying various security measures to minimize potential attack surfaces and secure the overall environment.

The correct choice outlines an activity that is not directly related to the standard practices of system hardening. Compiling code for applications, while important in the broader software development and deployment context, is not typically categorized as a step in system hardening. System hardening primarily focuses on configuring and securing existing systems rather than altering the underlying code or how applications are built.

On the other hand, enforcing least privilege management restricts user permissions to only what is necessary for their role, thus minimizing the potential damage from credential misuse. Removing unnecessary ports and services eliminates avenues through which attackers could gain access, and implementing patch management ensures that known vulnerabilities are addressed in a timely manner. These are essential strategies in strengthening system security, making them integral to the hardening process.