CEH v13 explains that Windows systems running older or default configurations often allow anonymous or null session connections to IPC$ shares, enabling attackers to enumerate users, groups, shares, and other system details without authentication. Null session enumeration is highlighted as a classic yet effective technique because it generates minimal detectable activity and does not require credentials, making it ideal for stealth operations. CEH stresses that SMB null sessions are frequently overlooked in legacy or poorly hardened environments, especially when default permissions remain unchanged. Packet sniffing (Option A) may provide some data but requires traffic visibility and may be detected through monitoring tools. DNS zone transfers (Option B) require misconfigurations and usually do not reveal user list details. SNMP queries (Option D) require community strings and often generate alerts. Therefore, exploiting null sessions is the most covert and effective method for enumerating Windows systems under default configurations.