In keeping with the layered defense model, barriers were developed at several system levels. DNS is a hierarchically organized collection of servers that maintain mappings between domain and host names and numerical Internet addresses. Securing this important information against potential compromise entailed the development of technology to efficiently authenticate transactions involving name- address mappings between DNS components. Middleware, a software layer interposed between applications and operating systems that allows applications to be distributed across multiple hosts of potentially different types, is becoming an increasingly important paradigm for distributed computing. Current technology, however, does not support extending such distributed applications across enclaves protected by firewalls and governed by different security policies.
Access is mediated by a firewall-like gateway, which also authenticates external requests.
As an example of accomplishment in operating system security, consider the Fluke OS project at the University of Utah. The central idea of Fluke is the Nested Process Model in which a parent process has strict control over the resource consumption of its children. The innovation in Fluke is that this is done very efficiently, allowing the imposition of security functionality where the performance penalty might otherwise be considered prohibitive. In the example, a security manager process is used to encapsulate the behavior of an untrusted application, while a trusted one is allowed to interact directly with the process manager. The Information Survivability Program also pioneered the concept of wrapper technology for inserting security at the application level.