The reported issues suggest problems related to network connectivity, remote access, and certificate management:
* A. Review VPN throughput: Connectivity issues and the inability to download applications while working remotely may be due to VPN bandwidth or performance issues. Reviewing and optimizing VPN throughput can help resolve these problems by ensuring that remote users have adequate bandwidth for accessing corporate resources.
* F. Validate MDM asset compliance: Mobile Device Management (MDM) systems ensure that mobile endpoints comply with corporate security policies. Validating MDM compliance can help address issues related to the inability to download applications and certificate errors, as non-compliant devices might be blocked from accessing certain resources.
* B. Check IPS rules: While important for security, IPS rules are less likely to directly address the connectivity and certificate issues described.
* C. Restore static content on the CDN: This action is related to content delivery but does not address VPN or certificate-related issues.
* D. Enable secure authentication using NAC: Network Access Control (NAC) enhances security but does not directly address the specific issues described.
* E. Implement advanced WAF rules: Web Application Firewalls protect web applications but do not address VPN throughput or mobile device compliance.
References:
* CompTIA Security+ Study Guide
* NIST SP 800-77, "Guide to IPsec VPNs"
* CIS Controls, "Control 11: Secure Configuration for Network Devices"

To design resilience in an enterprise system that can survive environmental catastrophes, recover within 24 hours, and be resilient to active exploitation, the best strategy is to allocate fully redundant and geographically distributed standby sites. Here's why:
* Geographical Redundancy: Having geographically distributed standby sites ensures that if one site is affected by an environmental catastrophe, the other sites can take over, providing continuity of operations.
* Full Redundancy: Fully redundant sites mean that all critical systems and data are replicated, enabling quick recovery in the event of a critical loss of availability.
* Resilience to Exploitation: Distributing resources across multiple sites reduces the risk of a single point of failure and increases resilience against targeted attacks.
* References:
* CompTIA Security+ SY0-601 Study Guide by Mike Chapple and David Seidl
* NIST Special Publication 800-34: Contingency Planning Guide for Federal Information Systems
* ISO/IEC 27031:2011 - Guidelines for Information and Communication Technology Readiness for Business Continuity