CEH v13 312-50v13 ECCouncil Study Notes

This scenario demonstrates SMTP Enumeration, a classic enumeration technique described in CEH v13 Network Enumeration. SMTP servers may expose commands such as VRFY, EXPN, and RCPT TO, which can be abused to validate user accounts.

When these commands are enabled without restriction, attackers can enumerate valid usernames without authentication. The Nmap script used explicitly leverages these commands, confirming the misconfiguration.

Option B is incorrect because authentication is not bypassed. Option C concerns DNS routing, not user enumeration. Option D relates to encryption, not enumeration capability.

CEH v13 strongly recommends disabling or restricting SMTP user verification commands. Thus, Option A is correct.

Once the base DN is identified through LDAP namingContexts, CEH teaches that the next step in enumeration is to query the directory tree using this DN. This allows retrieval of users, groups, computers, and other AD objects. LDAP-based enumeration requires valid search filters rooted in the base DN.

PKI uses public-key cryptography, which is widely used on the Internet to encrypt messages or

authenticate message senders. In public-key cryptography, a CA generates public and private

keys with the same algorithm simultaneously. The private key is held only by the subject (user,

company, or system) mentioned in the certificate, while the public key is made publicly available

in a directory that all parties can access. The subject keeps the private key secret and uses it to

decrypt the text encrypted by someone else using the corresponding public key (available in a

public directory). Thus, others encrypt messages for the user with the user's public key, and the user decrypts it with his/her private key.

The CEH Cloud Security module highlights identity and access management (IAM) failures as a major source of cloud breaches. Ensuring timely de-provisioning of user accounts when employees leave is a core security control.

Option C is correct.

Options A and B detect issues but don’t prevent access persistence.

Option D is unrelated to access control.

CEH stresses joiner–mover–leaver (JML) processes.