An obfuscating transformation aims at confusing a program in order to make it more difficult to understand while preserving its functionality. Software protection and malware detection are two major applications of code obfuscation. Software developers use code obfuscation in order to defend their programs against attacks to the intellectual property, usually called malicious host attacks. In fact, by making the programs more difficult to understand it is possible to obstruct malicious reverse engineering“ a typical attack to the intellectual property of programs. On the other side, malware writers usually obfuscate their malicious code in order to avoid detection. In this setting, the ability of code obfuscation to foil most of the existing detection techniques, such as misuse detection algorithms, relies in their purely syntactic nature that makes malware detection sensitive to slight modifications of programs syntax. In the software protection scenario, researchers try to develop sophisticated obfuscating techniques that are able to resist as many attacks as possible. In the malware detection scenario, on the other hand, it is important to design advanced detection algorithms in order to detect as many variants of obfuscated malware as possible. It is clear how both malicious host and malicious code attacks represent harmful threats to the security of computer networks.