What are best practices for IP allowlisting?

• A. Maintain current allowlists, require justification for exceptions, review regularly.
• B. Reduce allowlists to a minimum and avoid exceptions.
• C. Remove the allowlisting process and rely on password resets for access control.
• D. Maintain current allowlists, require justification for exceptions, review regularly, monitor for anomalies; have onboarding/offboarding processes.

Answer: (D)

IP allowlisting works best when it’s treated as a living control with ongoing governance. Keeping current allowlists helps ensure access is limited to known, trusted IPs and isn’t granted to outdated or unauthorized addresses. Requiring justification for any exceptions prevents drift, so temporary needs or ad hoc access don’t become permanent allowances. Regular reviews keep the list aligned with changes in personnel, infrastructure, and risk posture, reducing the chance of stale permissions. Monitoring for anomalies adds an active safety net—you can detect unusual patterns, such as logins from unexpected locations or at odd times, and respond quickly. Having onboarding and offboarding processes guarantees that new users receive appropriate access and that departing users are promptly removed, maintaining the principle of least privilege throughout the employee lifecycle. Taken together, these practices create a more secure, auditable, and responsive allowlisting program.

Other approaches miss key elements. Simply maintaining lists and requiring exceptions without monitoring or lifecycle processes leaves blind spots. Reducing allowlists and avoiding exceptions can impede legitimate needs and still expose risk. Removing allowlisting entirely in favor of password resets weakens access controls and increases the potential for credential compromise.