Refer to the exhibit.

When configuring Cisco Umbrella to block all traffic except to domains explicitly allowed (e.g., cisco.com), the “Allow-Only Mode” must be enabled. This setting overrides default behavior and ensures that only entries listed in the allow list are accessible—everything else is automatically blocked. According to SCAZT Section 1 (Cloud Security Architecture, Pages 16–19), enabling Allow-Only Mode is crucial for strict outbound DNS filtering.

Without this setting, the system allows access to all domains not explicitly blocked, which is why the engineer was able to access non-cisco.com domains despite defining an allow list.