Reversing - Secrets of Reverse Engineering

本文摘录自《Reversing: Secrets of Reverse Engineering》,详细介绍了五种主要恶意软件的定义:病毒,一种通常带有恶意目的的自我复制程序;蠕虫,通过网络自我复制且不需要直接人为交互的恶意程序;特洛伊木马,表面上无辜但实际上隐藏恶意元素的程序;后门,为攻击者创建隐蔽通道以控制或监视受害系统的软件;广告软件,强制向最终用户显示未经请求的广告并收集用户浏览习惯的程序。

 << Reversing - Secrets of Reverse Engineering >> 是一本关于逆向工程不可多得的好书,谈到了逆向工程的方方面面,如果你有一定的编程经验,对汇编程序不反感,又想了解逆向工程的话,我强烈推荐您读这本书(网上可下载)。

这里仅摘录书中关于恶意软件分类的定义。

malicious software category


    Viruses : self-replicating programs that usually have a malicious intent.


    Worms: fundamentally similar to a virus in the sense that it is a self-replcating malicious program. The         difference is that a worm self-replicates using a netword(such as the Internet), and the replication process doesn't require direct human interaction.


    Trojan Horese: The general idea is that a Trojan horse is an innocent artifact openly delivered through the front door when it in fact contains a malicous element hidden somewhere inside of it.


    Backdoors: A backdoor is a type of malicious software that creates a(usually covert) access channel that the attaker can use for connecting,controlling,spying,or otherwise interacting with the victim's system.  

                    
    Adware: Adware is programs that force unsolicited advertising on end users. Gathers various statistics regarding the end user's browsing and shopping habits(sometimes transmitting that data to a centralized server) and uses that information to display targeted ads to the end user.
          

### CTF Reversing x64 ELF 100 Challenge Solution and Hints For the reversing challenge involving an x64 ELF file, understanding how to interpret hexadecimal strings as ASCII characters is crucial. When faced with a string that appears nonsensical at first glance but contains digits from `0` through `F`, it suggests dealing with hexadecimal encoding. Converting such hex values into their corresponding ASCII representations can reveal hidden messages or flags required by challenges. In this specific case, converting each pair of hexadecimal digits (like `66`) into decimal yields ASCII codes which translate directly into readable text characters; for instance, `66` becomes `102` in decimal, representing 'f' according to the ASCII standard[^1]. Following similar conversions (`6c` -> `110` -> 'n'), one might deduce part of the flag format expected within these types of puzzles—often enclosed between curly braces following "flag". Regarding handling ELF files specifically, knowledge about the structure including headers like `ELF64_Ehdr` and sections described via structures such as `ELF64_Shdr` proves beneficial when attempting reverse engineering tasks on binaries formatted under the Executable and Linkable Format specification used primarily across Unix-like systems[^2]. To tackle this particular level effectively: - Examine any provided binary using tools designed for analyzing ELF executables. - Look out for embedded strings or data segments containing potential clues encoded similarly to what was discussed earlier regarding hexadecimal-to-text conversion. - Utilize debugging utilities alongside disassemblers to trace execution flow while paying attention to operations manipulating input/output streams where flags could be checked against user-supplied answers during runtime. ```bash # Example command line tool usage for inspecting ELF binaries readelf -h your_binary_file # Display the ELF header information strings your_binary_file # Extract printable character sequences possibly hinting towards solutions ``` --related questions-- 1. What are common methods employed in decoding obfuscated texts found inside executable programs? 2. How does one approach decompiling or disassembling different architectures beyond just x86_64? 3. Can you explain more about the significance of various fields present within the ELF header concerning program loading and linking processes?
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