Microsoft Security Advisory: Vulnerability in TLS/SSL could allow spoofing
This update is not a security update that end-users can install. Instead, this update is recommended for server administrators only. This update deploys a workaround that disables Transport Layer Security (TLS) and Secure Sockets Layer (SSL) renegotiation support on affected systems to help protect clients that connect to such servers from exploitation by using this vulnerability.
TLS renegotiation is a component of the Transport Layer Security protocol and may be required by certain applications. We recommend that customers validate the need for implementing this workaround, and if it is considered required, test this workaround carefully for the applicable deployment scenario or scenarios.
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB977377.