Polymorphic Worm Detection Using Structural Information of Executables

Abstract. Network worms are malicious programs that spread auto-matically across networks by exploiting vulnerabilities that a ect a large number of hosts. Because of the speed at which worms spread to large computer populations, countermeasures based on human reaction time are not feasible. Therefore, recent research has focused on devising new techniques to detect and contain network worms without the need of human supervision. In particular, a number of approaches have been proposed to automatically derive signatures to detect network worms by analyzing a number of worm-related network streams. Most of these techniques, however, assume that the worm code does not change during the infection process. Unfortunately, worms can be polymorphic. That is, they can mutate as they spread across the network. To detect these types of worms, it is necessary to devise new techniques that are able to identify similarities between di erent mutations of a worm. This paper presents a novel technique based on the structural analy-sis of binary code that allows one to identify structural similarities be-tween di erent worm mutations. The approach is based on the analysis of a worm's control flow graph and introduces an original graph coloring technique that supports a more precise characterization of the worm's structure. The technique has been used as a basis to implement a worm detection system that is resilient to many of the mechanisms used to evade approaches based on instruction sequences only.