Prevent "Ghost Calls" on Polycom VVX Series

Prevention via best networking practices:

  • Disable SIP ALG
  • Disable DMZ
  • Disable Port-Forwarding ports used for SIP (example 5060)

If the above mentioned methods fail, implement “Incoming Signaling Validation” in the Polycom’s configuration file. This will prevent the phone from responding to malicious SIP INVITEs.

Config:

<voIpProt.SIP.requestValidation voIpProt.SIP.requestValidation.1.method="source" voIpProt.SIP.requestValidation.1.request="INVITE" ></voIpProt>

After the phone pulls it’s new config, all incoming calls that do not match the reg.1.server.1.address="" Value will receive a 400 Bad Request SIP Message from the phone.

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