The HTTP fallback for SIP connection in Lync must be disabled.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
| V-223345 | O365-LY-000002 | SV-223345r1043178_rule | CCI-001184 | medium |
| Description | ||||
| Prevents from HTTP being used for SIP connection in case TLS or TCP fail. | ||||
| STIG | Date | |||
| Microsoft Office 365 ProPlus Security Technical Implementation Guide | 2025-03-05 | |||
Details
Check Text (C-223345r1043178_chk)
Verify the policy value for Computer Configuration >> Administrative Templates >> Skype for Business 2016 >> Microsoft Lync Feature Policies "Disable HTTP fallback for SIP connection" is set to "Enabled".
Use the Windows Registry Editor to navigate to the following key:
HKLM\Software\Policies\Microsoft\office\16.0\lync
If the value disablehttpconnect is REG_DWORD = 1, this is not a finding.
Fix Text (F-25006r442255_fix)
Set the policy value for Computer Configuration >> Administrative Templates >> Skype for Business 2016 >> Microsoft Lync Feature Policies "Disable HTTP fallback for SIP connection" to "Enabled".