Decompiling .NET Assemblies

As mentioned earlier, .NET assemblies are compiled into MSIL. Because MSIL is then compiled by the CLR, generally it is easy to decompile an assembly to reveal something that almost resembles the original source code. When you are looking for certain types of security vulnerabilities, using a decompiler is extremely useful, for example, to find luring attacks by discovering which methods do a demand for a permission versus the ones that dont. To make it harder for an application to be decompiled, the assembly can be obfuscated a process that involves mangling the programming logic, but not changing the runtime behavior of the application. Chapter 17, Observation and Reverse Engineering, discusses how a program can be reverse engineered to enable an attacker to discover the program logic that can be used to discover flaws in the software or even bypass certain security checks.