Taxonomy of web-based malware - finding rules for heuristic detection presented at Virus Bulletin 2008

by Fraser Svajcer (Sophos),

Tags: Security


Summary : Scripts embedded in HTML pages have been responsible for a large proportion of wide-scale malware attacks. Wide
accessibility of vulnerable web applications combined with a significant number of unpatched browser and browser
plug-in vulnerabilities has provided fertile ground for delivery of malware. Web-based threats are constantly changing
in nature and complexity, with new obfuscation techniques and payload delivery methods appearing daily.
Yet, the large proportion of existing work on classifying and taxonomy of malware concentrates mostly on Windows
executables. The intention of this paper is to provide the reader with a useful classification of web-based script threats
based on the well defined attributes of the current malicious set of scripts.
The paper discusses the results of various script analysis methods with the objective of classifying web-based script
malware and discovering attributes that can safely be used to construct heuristic detection rules, with the emphasis on
minimising false positive detections. The suitability of discovered attributes is verified using statistical and
machine-learning methods.
The research also documents various threat characteristics including the most commonly used attack methods, delivery
methods, delivered payloads, size of distribution networks, obfuscation methods, geographic locality, delivered
exploits and shellcode, number of exploits per attack site and number of attacks per compromised site. The presentation
will include case studies and a demonstration of a web threat analysis system.