SMB Signing is a Microsoft-devised security mechanism that attempts to prevent man-in-the-middle atacks.
This feature available under the CIFS Proxy, when enabled the signatures are added to the packet header while the user uses the CIFS proxy.
It is noticed that the User name and password entered post enabling the SMB credential in Proxy SG version 6.2.x does not get populated.
NOTE: This issue has been reported to Bluecoat Engineering. If you see this issue, please log a Service Request, and quote this article