Stepping stone (computer security)

A stepping stone (StSt) is a type of computer security measure which consists of placing several logical security systems used as authentication servers in a serial disposition to emulate a physical narrow channel like a physical path formed by stones used to cross a river. Using this system it is possible to apply a granular control over each system acting as a 'stone' establishing so different risk levels as so many systems which it have been placed. I.e. If we need grant to a user access to an OpenSSH server to execute an application in a high security environment we could put a front-end system such as a Sun Solaris with Citrix Metaframe in the 1st security layer. Behind a MS Terminal Services with a SSH Client. thirdly, the last layer based on a Linux System with an OpenSSH Server which will grant access to the final application. Every system could to have a common secure system to log on as RSA SecureID, X.509 certificates based, challenge/response systems, etc. or a mixture of them. It will depends on the risk analysis over the environment treated. This computer security practices makes difficult the system usability and is hard to maintain so only should be implemented in high security environments. This practices could be considered as part of well known security principle:Security In-Depth, in this case, applied to the access control, adding logical barriers and trenches, composed by diverse authentication systems.