Obfuscating code

The Laudanum shell generated by CO2 in the previous section worked just fine, but if a defender looks a little too closely at the source code, it will definitely raise some red flags. Ideally, we want to keep the file size as small as possible and try to make the code more difficult to analyze. The comments, the properly indented code, and descriptive variable names make figuring out what ads.php actually does a breeze.

Let's make analysis a bit more complicated. Code obfuscators are commonly used in digital rights management software, anti-piracy modules, and of course, malware. While no code obfuscator will stop an experienced reverse engineer, it certainly does slow things down; perhaps long enough for us to move on to another server or application, but at least long enough to evade antivirus signatures. Ideally, we remove the comments, rename the variables, and try to hide the shell's actual functionality, but it's not a good idea to do this manually. Human error can...