Which of the following would be the BEST mitigation practice for man-in-the-middle (MITM) Voice over Internet Protocol (VoIP) attacks?

MGCP is a VoIP signaling protocol that controls media gateways but does not inherently provide encryption or authentication, making it insufficient as a MITM mitigation technique on its own.

Transport Layer Security (TLS) encrypts VoIP signaling protocols such as SIP, preventing attackers from intercepting, tampering with, or replaying call setup and teardown messages in a MITM attack. When combined with SRTP (Secure Real-time Transport Protocol) for media, TLS provides comprehensive protection for both the signaling and data planes of VoIP communications, directly addressing MITM vulnerabilities.

FTP is a file transfer protocol with no relevance to VoIP communications or MITM attack mitigation, and it actually transmits data in cleartext, making it vulnerable to interception itself.

SSH secures remote command-line access to network devices but does not encrypt VoIP signaling or media streams, so it does not directly mitigate MITM attacks targeting VoIP sessions.