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CS0-003 · Question #593

An IDS is triggered during after-hours operations. The indicator records an abnormal amount of SYN requests being sent to port 21 from numerous external systems. A security analyst reports this…

The correct answer is D. A DDoS attack through the FTP port. Port 21 is used for FTP. An abnormal number of SYN requests from many external systems indicates a SYN flood, a type of Distributed Denial of Service (DDoS) attack targeting the FTP service to overwhelm the server and disrupt availability.

Submitted by devops_kid· Mar 6, 2026Incident Response and Management

Question

An IDS is triggered during after-hours operations. The indicator records an abnormal amount of SYN requests being sent to port 21 from numerous external systems. A security analyst reports this information to the IR team for further investigation. Which of the following best describes this incident?

Options

  • AA sniff attack through the DNS port
  • BA buffer overflow attack through the Telnet port
  • CA reconnaissance attack through the SSH port
  • DA DDoS attack through the FTP port

How the community answered

(46 responses)
  • A
    15% (7)
  • B
    4% (2)
  • C
    9% (4)
  • D
    72% (33)

Explanation

Port 21 is used for FTP. An abnormal number of SYN requests from many external systems indicates a SYN flood, a type of Distributed Denial of Service (DDoS) attack targeting the FTP service to overwhelm the server and disrupt availability.

Topics

#DDoS#SYN flood#IDS alert#FTP#port 21

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