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SY0-501 · Question #247

A security analyst wants to harden the company's VoIP PBX. The analyst is worried that credentials may be intercepted and compromised when IP phones authenticate with the BPX. Which of the following…

The correct answer is D. Require SIPS on connections to the PBX. To prevent the interception and compromise of authentication credentials during IP phone authentication with a PBX, implementing SIPS (SIP Secure) is the most effective solution.

Submitted by skyler.x· Mar 4, 2026Security architecture

Question

A security analyst wants to harden the company's VoIP PBX. The analyst is worried that credentials may be intercepted and compromised when IP phones authenticate with the BPX. Which of the following would best prevent this from occurring?

Options

  • AImplement SRTP between the phones and the PBX.
  • BPlace the phones and PBX in their own VLAN.
  • CRestrict the phone connections to the PBX.
  • DRequire SIPS on connections to the PBX.

How the community answered

(34 responses)
  • A
    12% (4)
  • B
    3% (1)
  • C
    6% (2)
  • D
    79% (27)

Why each option

To prevent the interception and compromise of authentication credentials during IP phone authentication with a PBX, implementing SIPS (SIP Secure) is the most effective solution.

AImplement SRTP between the phones and the PBX.

SRTP (Secure Real-time Transport Protocol) encrypts the media stream (audio/video payload) but does not secure the SIP signaling traffic where authentication credentials are exchanged.

BPlace the phones and PBX in their own VLAN.

Placing devices in a VLAN provides network segmentation but does not encrypt the communication channel itself, leaving credentials vulnerable if sniffed within the VLAN.

CRestrict the phone connections to the PBX.

Restricting phone connections is a general access control measure that limits who can connect but does not inherently encrypt the traffic or prevent credential interception once a connection is established.

DRequire SIPS on connections to the PBX.Correct

SIPS (Session Initiation Protocol Secure) utilizes Transport Layer Security (TLS) to encrypt the signaling channel between the IP phone and the PBX. This encryption protects sensitive information, including authentication credentials, from being intercepted and compromised during the authentication process and subsequent call setup.

Concept tested: VoIP signaling security protocols (SIPS/TLS)

Source: https://learn.microsoft.com/en-us/microsoftteams/teams-security-guide#sip

Topics

#VoIP security#SIPS#credential protection#protocol security

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