Which of the following techniques can reveal misconfigured DNS settings?

Performing zone transfers is a technique that can effectively reveal misconfigured DNS settings. Zone transfers occur when a domain name server (DNS) allows the transfer of its entire DNS database to another server. This typically happens when a secondary DNS server is configured to update itself from the primary server. Properly configured DNS servers restrict zone transfers to designated servers. However, if the server is misconfigured and allows unauthorized access, an attacker or a tester can retrieve sensitive information about all the DNS records associated with that domain, including subdomains, IP addresses, and other data that should not be publicly accessible.

This capability enables both legitimate security assessments and malicious actors to gather information on the organization's network topology and services. Therefore, identifying such misconfigurations through zone transfers is a critical step in assessing network security and strengthening the DNS infrastructure.

Other techniques listed, while associated with information gathering in different contexts, do not directly focus on revealing DNS misconfigurations. Identifying valid email addresses might help in understanding the organization's communication infrastructure, analyzing SMTP headers can provide insight into email routing and delivery, and locating the organization's web presence can show what services are available online, but none of these methods directly address vulnerabilities or configurations regarding DNS settings as clearly as performing zone transfers does.