Detecting and Countering System Intrusions Using Software Wrappers

This paper introduces an approach that integrates intrusion detection (ID) techniques with software wrapping technology to enhance a system's ability to defend against intrusions. In particular, we employ the NAI Labs Generic Software Wrapper Toolkit to implement all or part of an intrusion detection system as ID wrappers. An ID wrapper is a software layer dynamically inserted into the kernel that can selectively intercept and analyze system calls performed by processes as well as respond to intrusive events. We have implemented several ID wrappers that employ three di erent major intrusion detection techniques. Also, we have combined di erent ID techniques by composing ID wrappers at run-time. We tested the individual and composed ID wrappers using several existing attacks and measured their impact on observed application performance. We conclude that intrusion detection algorithms can be easily encoded as wrappers that perform eÆciently inside the kernel. Also, kernel-resident ID wrappers can be easily managed, allowing cooperation among multiple combined techniques to enforce a coherent global ID policy. In addition, intrusion detection algorithms can bene t from the extra data made accessible by wrappers.