Which of the following concepts will help lower the attack surface after unauthorized user-level access?

 Hardening is the concept that will help lower the attack surface after unauthorized user-level access. Hardening is the process of securing a system by reducing its vulnerability to attacks. Hardening involves applying patches, updates, and configuration changes to eliminate or mitigate known weaknesses. Hardening also involves disabling or removing unnecessary services, features, and accounts that could be exploited by attackers. Hardening can help lower the attack surface by reducing the amount of code running, the number of entry points available, and the potential damage that can be caused by unauthorized access. References: CompTIA Cloud Essentials+ CLO-002 Study Guide, Chapter 4: Cloud Security, Section 4.2: Cloud Security Concepts, Page 153.