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CompTIA

SK0-004 · Question #830

A server technician was recently given a penetration testing report. The report states that VNC is running on server 192.168.1.25. Which of the following can the technician conclude about the…

The correct answer is C. The default TCP port for VNC is 5900, and the penetration test is implying the system can be. VNC (Virtual Network Computing) listens on TCP port 5900 by default, not port 3389 which belongs to Microsoft RDP. A penetration test finding VNC active indicates the server is exposed to remote graphical control.

Security and disaster recovery

Question

A server technician was recently given a penetration testing report. The report states that VNC is running on server 192.168.1.25. Which of the following can the technician conclude about the statement?

Options

  • AThe default TCP port for VNC is 3389, and the penetration test is implying the system cannot
  • BThe default TCP port for VNC is 3389, and the penetration test is implying the system can be
  • CThe default TCP port for VNC is 5900, and the penetration test is implying the system can be
  • DThe default TCP port for VNC is 5900, and the penetration test is implying the system cannot

How the community answered

(21 responses)
  • A
    10% (2)
  • C
    86% (18)
  • D
    5% (1)

Why each option

VNC (Virtual Network Computing) listens on TCP port 5900 by default, not port 3389 which belongs to Microsoft RDP. A penetration test finding VNC active indicates the server is exposed to remote graphical control.

AThe default TCP port for VNC is 3389, and the penetration test is implying the system cannot

Port 3389 is the default for Microsoft Remote Desktop Protocol, not VNC - VNC uses port 5900, so this answer contains a factual error about the protocol assignment.

BThe default TCP port for VNC is 3389, and the penetration test is implying the system can be

While the conclusion about remote access is directionally correct, the stated port of 3389 is incorrect for VNC, making this answer technically wrong despite its partial accuracy.

CThe default TCP port for VNC is 5900, and the penetration test is implying the system can beCorrect

VNC is assigned TCP port 5900 by IANA as its default listening port, which is entirely separate from RDP's port 3389. A penetration test reporting VNC as running means the service is active and the server can be remotely viewed and controlled, representing a potential unauthorized access vector if the service is unintended or improperly secured.

DThe default TCP port for VNC is 5900, and the penetration test is implying the system cannot

A running VNC service means remote access IS possible - an active listening service implies reachability, not the inability to be accessed.

Concept tested: VNC default port and remote access security implications

Source: https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml

Topics

#VNC#penetration testing#TCP ports#remote desktop

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