The first action is to implement continuous and context-based authentication and authorization (A).
Traditional authentication validates users only at login, which creates gaps during active sessions. Continuous authentication ensures validation throughout the data access workflow, incorporating contextual factors like device state, geolocation, and behavioral analysis. This directly aligns with audit findings requiring protection by role, identity validation, and action tracking.
Option B improves onboarding and monitoring but does not enforce continuous access control. Option C improves identity federation but does not provide session-by-session validation. Option D secures APIs but is too narrow for organization-wide identity workflows.
CAS-005 stresses Zero Trust and context-aware IAM, making continuous authentication and authorization the top priority.

The Subject Alternative Name (SAN) field in an X.509 certificate specifies additional hostnames, FQDNs, or IP addresses that the certificate will secure. To allow mutual TLS authentication for multiple hostnames and an IP address, these identities must be included in the SAN field.
* Organizational Unit (B) is an informational attribute, not related to TLS authentication.
* Extended Key Usage (C) defines purpose (e.g., serverAuth, clientAuth) but not hostnames.
* "Certificate extension" (D) is a generic term; SAN is the specific required extension.

* A. Implementing allow lists: Allow lists (whitelisting) restrict network communication to only authorized devices and applications, significantly reducing the attack surface by ensuring that only pre-approved traffic is permitted.
* F. Implementing a site-to-site IPSec VPN: A site-to-site VPN provides a secure, encrypted tunnel for data transmission between the OT systems and the vendor, protecting the data from interception and tampering during transit.
Other options:
* B. Monitoring network behavior: While useful for detecting anomalies, it does not proactively reduce the risk of compromise or sabotage.
* C. Encrypting data at rest: Important for protecting data stored on devices, but does not address network communication risks.
* D. Performing boot integrity checks: Ensures the integrity of the system at startup but does not protect ongoing network communications.
* E. Executing daily health checks: Useful for maintaining system health but does not directly reduce the risk of network-based compromise or sabotage.
References:
* CompTIA Security+ Study Guide
* NIST SP 800-82, "Guide to Industrial Control Systems (ICS) Security"
* "Industrial Network Security" by Eric D. Knapp and Joel Thomas Langill