Covert Data Exfiltration:

DNS traffic can be leveraged for covert data exfiltration because it is often allowed through firewalls and not heavily monitored.

Tools or techniques for DNS tunneling encode sensitive information into DNS queries or responses, resulting in an observable increase in DNS traffic.

Why Not Other Options?

B (URL spidering): This increases HTTP traffic, not DNS traffic.

C (HTML scrapping): Involves downloading website content, which primarily uses HTTP or HTTPS.

D (DoS attack): A DNS-based DoS attack would likely involve query floods from many sources, not necessarily related to the observed behavior in a penetration test.

CompTIA Pentest+ References:

Domain 3.0 (Attacks and Exploits)

Covert Communication Techniques and DNS Tunneling