It should be noted that all GSS security tokens are sent over the encrypted TLS channel.
This tokens can be NTL, Kerberos or PKI Authentication for Smart Cards.
Recently there has been a lot of attention given to the Remote Desktop Protocol for attacker.
The protocol has seen a work in 2011 that abused week passwords and it’s features to copy files and infect other machines and now in 2012 there is a remote code execution bug in the protocol it self.
The graphic bellow illustrates how this is done: Most brut force tools currently out there do not take in to account NLA, it would slow down the process even more and add another level of complexity.
Using the TLS connection as an encrypted channel; it does not rely on the client/server authentication services that are available in TLS but does uses it for validating identity.
The Cred SSP Protocol then uses the Simple and Protected Generic Security Service Application Program Interface Negotiation Mechanism (SPNEGO) Protocol Extensions to negotiate a Generic Security Services (GSS) mechanism that performs mutual authentication and GSS confidentiality services to securely bind to the TLS channel and encrypt the credentials for the target server.
The Smart Card Alliance is a not-for-profit, multi-industry association working to stimulate the understanding, adoption, use, and widespread application of smart card technology.Through specific projects such as education programs, market research, advocacy, industry relations, and open forums, the Alliance keeps its members connected to industry leaders and innovative thought.The Alliance is the single industry voice for smart cards, leading industry discussion on the impact and value of smart cards in the United States and Latin America.The Smart Card Alliance Identity Council is focused on promoting the need for technologies, legislation, and usage solutions regarding human identity information to address the challenges of securing identity information and reducing identity fraud, and to help organizations realize the benefits that secure identity information delivers.Since the days of Vista and Windows 2008 Microsoft has provided a new mechanism for securing RDP connections with what they call Network Level Authentication, this uses Microsoft Cred SSP Protocol to authenticate and negotiate credential type before handing off the connection to RDP Service.Cred SSP first establishes an encrypted channel between the client and the target server by using Transport Layer Security (TLS).