# Software Reversing ## System Level Reversing Observe how the software is provided and how it operates. * Involves analyzing the environment, packaging, and dependencies, and then observing behaviour. * May require tools to intercept traffic, system calls, and input/output. End goal: collect information to direct further analysis. * Important to select tools, processes, and overall strategy. * Language use, packaging algorithms, encryption * Important to characterize behaviour and identify external dependencies. * Remote servers involved, files accessed, communication channels used. ## Code Level Reversing Extract design concepts and algorithms from binaries. * Compiled to binary code or bytecode. It’s a complex, architecture-dependent process. * Some say “an art form”. * Expensive enough that competitive RE is not usually pursued. * To fully reverse and reassemble a given competing software (except in some cases). Makes use of tools capable of representing the low-level language in something “human compatible”. * Compiler optimization and obfuscation make this process uncertain. * Perfect reconstruction is frequently impossible as low-level languages do not use the same constructs as higher-level ones. ## Activities Understanding the processes. * Large-scale observation of the program at a process level. * Identification of major components and their functionality. Understanding the Data. * Understand the data structures used. Understanding Interfaces. * Which interfaces exist and how does the process react to them? ## Software Reversing Programs are developed in a high-level programming language. * C, C++, C#, Java, Python, Go… A compiler converts the high-level instructions to low-level instructions. * Machine Code: instructions that are executed directly by the CPU. * Bytecode: instructions that are executed by a middleware, VM or Interpreter. Reverse Engineering involves understanding low-level instructions. * Which is not easy and is costly. * Requires knowledge of the specific target being analyzed (the VM, the CPU). * Different CPUs have different opcodes and execution behaviour. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://davidjosearaujo.gitbook.io/notes-mcs/reverse-engineering/introduction-to-reverse-engineering/software-reversing.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.