Which of the following is a high-level method attackers use to exfiltrate data?

• A. Covert channels like DNS tunneling
• B. Password reuse
• C. Spam email
• D. Public Wi-Fi usage

Answer: (A)

Data exfiltration often relies on covert channels that blend with normal network activity. DNS tunneling is a classic example of this approach. Attackers encode sensitive data into DNS queries and send them to a domain they control. Because DNS traffic is widespread and frequently allowed through firewalls and proxies, it can slip past perimeter defenses that are focused on more obvious protocols. The attacker’s server collects these encoded queries and can return data in DNS responses, allowing information to be moved out of the network without triggering typical alerts. This method is powerful because it uses a trusted, ubiquitous service and can quietly transmit data over many small queries, gradually exfiltrating substantial information.

Other options don’t target data leaving the network in the same high-level, stealthy way. Password reuse is about compromising credentials, not exfiltrating data. Spam email can be used to leak information, but it’s generally easier to detect and less reliable for continuous, automated exfiltration. Public Wi‑Fi usage describes a location or condition, not a technique for exfiltration itself, though attackers might leverage any network under certain schemes.