You get the same benefit from debugging when reversing applications as you get from debugging live applications. OllyDbg and its successor x64dbg is probably the best debugger when it comes to software reverse engineering. It was specifically developed for the needs of reversing, and has all the tools needed for that purpose:. The ability to parse API functions and their parameters makes it easy to reverse interactions with a system. The stack view provides a lot of information about the call stack.
Despite its simple interface, WinDbg has powerful tools for debugging. Windbg Preview is a new version of Windbg developed by Microsoft. It has all the features of the classic Windbg coupled with a new UI and several new features. One of these new features is Time Travel Debugging, which allows you to record some period of program execution and then replay it as many times as you need.
This way, you can execute the interesting parts of the code by stepping, without being afraid to run some code accidentally and lose the context or all the data. Read also: 9 Best Reverse Engineering Tools for As we can see, this file creates a Windows service named TestDriver. But where does it take the driver file from in order to run? We can use ProcessMonitor from Sysinternals Suite to find out. Its activity log looks like this:. So what does the process do with this file?
For that purpose, we extract the resource using Resource Hacker and open it in the disassembler. As we know, DriverEntry is the entry point for kernel-mode drivers in Windows systems. To begin reverse engineering the driver, we examine functions that are called from DriverEntry one by one.
We found out that the original program extracts the driver file from its resources, puts it in the temp folder of the current user, creates the Windows service for this driver, and runs it. After that, the program stops and deletes the service and the original driver file from the temp directory.
We could have achieved this result in many different ways — using debugging or API Mon, writing tests, etc. You can find your own ways to reverse engineer software that work for you. Windows software reverse engineering requires a solid educational background and reverse programming experience. In order to perform reverse engineering, you need to combine skills in disassembling, network monitoring, debugging, API integration, several program languages, compilers, etc.
Now, to make jmp , we need to save the MessageBox address to esi. In Screenshot 35, you can see that there is an unconditional jump. If we run the application via the debugger, the application will crash because the previous command contains an absolute address, and after the application starts, the loader passes the relocation table and adds delta to each value to make all addresses valid.
What we need to do now is remove this value from the relocation table. Thus, we have to remove the A value from the relocation table. To do so, we need to open the current version of our test application with Relocation Section Editor. CFF Explorer can help us fix this issue. We have found the value — — on which delta for MessageBox used to be added. You can also add your own functions to API Monitor and use this tool to monitor network function calls and research passed parameters of course, if traffic is not encrypted.
So we select only them in User After running our process, we see the list of called functions. Also, we can set different breakpoints for a function:. Read also: Reverse Engineer Software. But before exploring a binary, we need to determine its type with a hex editor. In our example, we use WinHex. The MZ signature at the zero offset corresponds to PE format files executables or shared libraries , so this is an exe file or dll. Most file formats have unique signatures.
Instead, we'll dump its memory and try to run it. To do that, we open the packed executable file in IDA Pro. This time, we need to find the original entry point OEP into the application rather than the entry point of the packer. The pusha command saves general-purpose registers to the stack. In the end, there should be the popa command which pushes the stored register values. After the popa command, there is a jmp to the original point of entry. Below the popa command, there is jmp 40A, which will eventually move to the original entry point.
Now, we can try to follow jmp. However, IDA Pro displays another warning message:. In the process list, choose our application and put the OEP address into the field.
As a result, Scylla will show that the import table has been found. If we run our application now, it will crash, so we need to remove the relocation table. Next, we need to check whether the ImageBase is the same that the application loaded into memory. When applied properly, reverse engineering can help you strengthen the security and improve the performance of your solution.
However, quality reverse engineering is impossible without using the right set of tools and techniques. In this article, we covered some of the best reverse engineering software that our team of professional reversers uses when researching software. Most of these tools can only be used for solving specific tasks, but when combined, they provide you with all the capabilities necessary for extensive software analysis.
Want to see if reverse engineering is the right approach for your next project? Get in touch with us using the form below. By clicking OK you give consent to processing your data and subscription to Apriorit Blog updates. Related services Professional Reverse Engineering[a]. Screenshot 1. IDA Pro interface. Screenshot 2. CFF Explorer interface. Screenshot 3. Screenshot 4. WinHex interface. Screenshot 5. Hiew interface. To save this patched code, right click in code window, select copy to executables, all modifications, Copy All, Save File as PatchedCrackme.
A new tab for your requested boot camp pricing will open in 5 seconds. If it doesn't open, click here. Hi Ninj S3c, I would like to point out a few things regarding the first part of your article. I need to say that the title is a little bit misleading. This article refers exclusively into UPX unpacking, so I think you should have added this into your title. I could probably mention a few other things regarding the second part, but I think this is enough already. Just to make this clear, I am not trying to disrespect your or the effort you made for writing those lines.
However, I cannot ignore the fact that this article has nothing to offer and it is written in such way that makes someone question even if you really understand what you are talking about or you are just reproducing something you saw somewhere online.
Regards, kyREcon. I agree, this may not be a great article on RE but I am beginner and my approach may be too naive. I tried to write an introductory article and tried to explain each and every step in my best capability. So, as you can see a great article is not just about the level of the technical details, but the way those are delivered. Regards, KA. Your email address will not be published. Topics Reverse engineering Unpacking, reversing, patching Reverse engineering Unpacking, reversing, patching.
Posted: February 13, We've encountered a new and totally unexpected error. Get instant boot camp pricing. Thank you! In this Series. Unpacking, reversing, patching Kali Linux: Top 8 tools for reverse engineering Stacks and Heap Top 8 reverse engineering tools for cyber security professionals [updated ] Arrays, Structs and Linked Lists Reverse engineering obfuscated assemblies [updated ] Crack Me Challenge Part 4 [Updated ] Writing windows kernel mode driver [Updated ] Assembly programming with Visual Studio.
Active Oldest Votes. PYCs - I personally recommend Uncompyle2 for that. Improve this answer. Ange Ange 6, 2 2 gold badges 25 25 silver badges 62 62 bronze badges.
More up to date Uncompyle is at pypi. There is also help in this post: stackoverflow. How do you do number 1? Remko Remko 2, 2 2 gold badges 17 17 silver badges 28 28 bronze badges. I'm not sure binwalk is the right tool for this job.
It'd show you to the compressed sections of the executable, but the output would likely have a lot other false positives as well unless you point it to look for only compressed sections Especially if we know what we're looking for but don't know in which file it is. I didn't mean to propose binwalk as a complete solution modified my answer to indicate it's a first step — Remko. FYI, the link to binwalk seems flag as malicious website as of June Karsun false positive on a binary on my website, I've reported this to google and it seems to be ok again now thanks for letting me know — Remko.
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