Abstract
This paper presents a software toolkit that allows enhancing the fault tolerant characteristics of a user application running under a Windows NT platform through sets of interchangeable and customizable Fault Tolerant Interposition Agents (FTI Agents). Interposition Agents are non-application software programs executed in an intermediate layer between the software application and the Operating System in order to ‘wrap” the application software intercepting and possibly modifying, all the communications between the application and the surrounding hardware and software environment. The process is completely transparent to both the user application and the Operating System and allows achieving a high degree of software-based reliability in a wide variety of domains.