Which is a feature mentioned in the DNS security module?

Layer-4 monitoring refers to transport-layer network traffic inspection and is not a feature specific to the DNS security module.

Cisco Umbrella is a cloud-delivered DNS security service that intercepts and inspects DNS queries, blocking connections to malicious domains before a network connection is established. It is the core product in Cisco's DNS security module, using global DNS infrastructure to enforce security policies. Umbrella applies threat intelligence from Cisco Talos to identify and block malicious destinations at the DNS layer.

Real-time sandboxing is a threat analysis feature associated with platforms like Cisco Threat Grid, not the DNS security module.

Data Loss Prevention is a separate security discipline focused on preventing unauthorized data exfiltration, unrelated to DNS security.