Disable SSL 3.0 in Lync Server 2013 and Skype for Business Server 2015

According to Microsoft Security Advisory 3009008, a vulnerability was detected in SSL 3.0.

Since both Lync and Skype for Business are using certificates extensively,it is recommended to disable SSL 3 on all Front End servers and reverse proxy solutions used to publish the web services.

Disabling SSL 3.0 in Lync Server 2013:

https://blogs.technet.microsoft.com/uclobby/2014/10/22/disabling-ssl-3-0-in-lync-server-2013/

Action suggested:-

For Windows Servers, SSL 3.0 can be disabled by creating a registry key using the following steps:

1.            Open the Command Prompt using elevated permissions

2.            Run the following cmdlet: reg add “HKLM\System\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\SSL 3.0\Server” /v Enabled /t REG_DWORD /d 0 /f

3.            After changing this, a restart to the Lync Services will be enough to apply the new configuration:

Stop-CsWindowsService

Start-CsWindowsService

In case you need to rollback, simply remove the key and restart the Lync Services:

reg delete “HKLM\System\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\SSL 3.0\Server” /v Enabled