Certified Ethical Hacker (CEH v10) — Question 112

Port scanning can be used as part of a technical assessment to determine network vulnerabilities. The TCP XMAS scan is used to identify listening ports on the targeted system.
If a scanned port is open, what happens?

Answer options

• A. The port will ignore the packets.
• B. The port will send an RST.
• C. The port will send an ACK.
• D. The port will send a SYN.

Correct answer: A

Explanation

When using a TCP XMAS scan, if a port is open, it will not respond to the scan packets, effectively ignoring them. This behavior distinguishes open ports from closed ones, which would typically respond with an RST packet. Thus, options B, C, and D describe responses from closed or filtered ports, not open ones.