DNS-based threats, such as DNS tunneling, phishing, or malware command-and-control (C2) activities, are commonly used by attackers to exfiltrate data or establish malicious communications. Palo Alto Networks firewalls provide several mechanisms to address these threats, and the correct method is DNS sinkholing.

Why "DNS sinkholing" (Correct Answer D)?DNS sinkholing redirects DNS queries for malicious domains to an internal or non-routable IP address, effectively preventing communication with malicious domains. When a user or endpoint tries to connect to a malicious domain, the sinkhole DNS entry ensures the traffic is blocked or routed to a controlled destination.

DNS sinkholing is especially effective for blocking malware trying to contact its C2 server or preventing data exfiltration.

Why not "DNS proxy" (Option A)?A DNS proxy is used to forward DNS queries from endpoints to an upstream DNS server. While it can be part of a network's DNS setup, it does not actively stop DNS-based threats.

Why not "Buffer overflow protection" (Option B)?Buffer overflow protection is a method used to prevent memory-related attacks, such as exploiting software vulnerabilities. It is unrelated to DNS-based threat prevention.

Why not "DNS tunneling" (Option C)?DNS tunneling is itself a type of DNS-based threat where attackers encode malicious traffic within DNS queries and responses. This option refers to the threat itself, not the method to stop it.