[Reference: SELinux is a powerful tool often covered in CASP+ material, but its OS-specific nature makes it unsuitable here., B. MDM (Mobile Device Management): MDM solutions are primarily used to manage mobile devices (smartphones, tablets). While some MDM solutions offer application control features, they are not designed for comprehensive application control across all OS types (including desktops)., Reference: MDM is relevant to CASP+ in the context of mobile security, but it's not the best fit for this cross-platform application control requirement., C. XDR (Extended Detection and Response): XDR is a threat detection and response platform that integrates multiple security products. While important for security, it's not designed to enforce application controlpolicies., Reference: XDR is a key component of modern security architectures and is covered in CASP+, but its focus is threat detection, not preventative application control., D. Allow List (Corrected from "Block List"): An allow list (also known as an application whitelisting) is a security mechanism that explicitly lists applications authorized to run. All other applications are blocked by default. This directly aligns with the "deny-all, permit-by-exception" approach., Reference: Allow lists (whitelisting) are a fundamental security control emphasized in CASP+. They are a core component of application control strategies., E. Atomic execution: This is not a recognized security control or term related to application control., Why D (Corrected to Allow List) is the Correct Answer:, An allow list perfectly implements the required security policy. By defining a list of approved applications, the organization ensures that only those applications can execute., This approach is effective across different operating systems, as long as the OS has a mechanism to implement application allow lists (most modern OSs do)., CASP+ Relevance: Allow listing is a critical security control discussed in CASP+ as a method to reduce the attack surface, prevent malware execution, and enhance endpoint security., Implementation Considerations (Elaboration based on CASP+ principles):, Creating the Allow List: This requires careful planning and inventorying of all necessary applications., Enforcement Mechanisms: Different OSs have different tools for enforcing application control policies. Windows has AppLocker, macOS has its own mechanisms, and various third-party endpoint security solutions also provide this functionality., Updating the Allow List: A process must be in place to add new applications to the allow list when needed, ensuring proper vetting and authorization., Exceptions: There might be a need for exceptions for certain users or systems, requiring careful consideration and management., In conclusion, an allow list (application whitelisting) is the most appropriate solution to implement a "deny-all, permit-by-exception" application control policy across all operating systems. It's a powerful security control aligned with the principles of least privilege and is a core concept covered in the CASP+ exam objectives. It is implied that the question was intended to be Allow List, but as written, Block List is the only reasonable answer., , , ]