Multi-stage delivery of malware

Malware signature detectors use patterns of bytes, or variations of patterns of bytes, to detect malware attempting to enter a systems. This approach assumes the signatures are both or sufficient length to identify the malware, and to distinguish it from non-malware objects entering the system. We describe a technique that can increase the difficulty of both to an arbitrary degree. This technique can exploit an optimization that many anti-virus systems use to make inserting the malware simple; fortunately, this particular exploit is easy to detect, provided the optimization is not present. We describe some experiments to test the effectiveness of this technique in evading existing signature-based malware detectors.