Manual unpack upx

In this tutorial, you will learn how to unpack any UPX packed Executable file using OllyDbg UPX is a free, portable, executable packer for several different executable formats.

If you already have UPX packed binary file then proceed further. Before we begin with unpacking exercise, lets try to understand the working of UPX. Based on type and complexity of Packer, unpacking operation may vary in terms of time and difficulty. UPX is the basic Packer and serves as great example for anyone who wants to learn Unpacking.

Here is the screenshot of OllyDbg in action. Usually this is the first instruction or it will be present after first few instructions based on the UPX version. Once you set up the breakpoint, continue the execution press F9. Now start step by step tracing with F7 and soon you will encounter a JMP instruction which will take us to actual OEP in the original program.

It will automatically fix all the Import table as well. That is it, you have just unpacked UPX!!! Now launch the ImpREC tool and select the process that you are currently debugging. Now click on 'Get Imports' to retrieve all the imported functions.

You will see all the import functions listed under their respective DLL names. Now run the final fixed executable to see if everything is alright.

Here are the steps shown in video. Email This BlogThis! Share to Twitter Share to Facebook. Newer Post Older Post Home. Subscribe to: Post Comments Atom. Popular Posts. How to get the serial number of a program with OllyDbg. One of the tests consisted of g You already know that the malware developers create packed executables in order to try to thwart the security analyst job and make a ligh Extracting files from a network traffic capture PCAP.

When we are involved in an incident handling and we are in charge of analyzing a traffic capture in a pcap format related to an attack, one A Network Traffic Analysis Exercise. Network forensics is something we should practice as much as possible to become faster at detecting supicious activies in our networks.

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Sucuri Blog. Palo Alto Networks Blog. It is basically an entire PE file loaded in memory in the same way that would be if we had read the file from disk into a buffer. Figure 1 — Memory Map. After we have dumped the UPX-packed malware from memory we can directly load this back to the debugger since it is basically a fully functional PE file.

In summary, the custom packing layer is totally out of the game at this point. Nothing really interesting here, apart from the fact that if you are familiar with UPX you can easily identify what you are dealing with.

Finding your way to the original entry point of the packed application is really easy. All you need to do is to scroll down the code until you find the following instructions. Place BP here and run. Figure 2 — OllyDump Plugin. Going through the process of manually unpacking and isolating the original malware from the top protection layers might not be something that you will always need to do in order to have an overview of what a malware sample is doing.

However, when more detailed analysis is needed for sophisticated and complex malware, having the original executable isolated from all the packing layers might be a privilege rather than just a convenience.