Reverse Engineering using OllyDgb and Resource Hacker (For educational purpose only)

Reverse Engineering

The reproduction of another manufacturer's product following detailed examination of its construction or composition.

Reverse engineering is taking apart an object to see how it works in order to duplicate or enhance the object. The practice, taken from older industries, is now frequently used on computer hardware and software. Software reverse engineering involves reversing a program's machine code (the string of 0s and 1s that are sent to the logic processor) back into the source code that it was written in, using program language statements.

When Reverse Engineering is used?

Reverse-engineering is used for many purposes: as a learning tool; as a way to make new, compatible products that are cheaper than what's currently on the market; for making software interoperate more effectively or to bridge data between different operating systems or databases; and to uncover the undocumented features of commercial products. 

Reverse engineering is needed whenever the documentation is lost or it never existed. Having the source helps.

In software design, reverse engineering enables the developer or programmer to add new features to the existing software with or without knowing the source code. Different techniques are used to incorporate new features into the existing software.

Disassembler

A disassembler is a computer program that translates machine language (Machine languages are the only languages understood by computers) into assembly language (A programming language that is once removed from a computer's machine language. Machine languages consist entirely of numbers and are almost impossible for humans to read and write. Assembly languages have the same structure and set of commands as machine languages, but they enable a programmer to use names instead of numbers.) The inverse operation to that of an assembler. A disassembler differs from a decompiler, which targets a high-level language rather than an assembly language.

 The debugger we are going use here is OllyDbg

 Decompiler

A decompiler is a programming tool that converts an executable program or low-level/machine language into a format understandable to software programmers.

Compiler

A compiler is a software program that transforms high-level source code that is written by a developer in a high-level programming language into a low level object code (binary code) in machine language, which can be understood by the processor.

Obfuscation

Obfuscation, in general, describes a practice that is used to intentionally make something more difficult to understand. In a programming context, it means to make code harder to understand or read, generally for privacy or security purposes. A tool called an obfuscator is sometimes used to convert a straight-forward program into one that works the same way but is much harder to understand.

C, C++ and Perl are among the languages usually considered to lend themselves to obfuscation. Java byte code is easy to decompile and thus vulnerable to reverse engineering. The code is often obfuscated to protect it from such an attack.

OllyDgb

OllyDbg is a 32-bit assembler level analyzing debugger for Microsoft Windows that emphasis on binary code analysis. Named after its author, Oleh Yuschuk it traces registers, recognizes procedures, API calls, switches, tables, constants and strings, as well as locates routines from object files and libraries.

Registration

This software is a shareware. To use this program on a permanent basis or for commercial purposes, you should register it by sending filled https://www.ollydbg.de/register.txt to Ollydbg@t-online.de. The registration is free of charge and assumes no financial or other obligations from either side - just be fair.

The write up is for educational purposes only

If you want to continue - Download Ollydbg 32 bit and install the program

Now open Ollydbg & press C which opens CPU. You will notice 4 windows coming up

Open new file which you want to change and right click on the first window and look for "search for" option and click on "All referenced text strings"

Now you can see the new file is made, right click and search for the option "Search for text"

On search for text write REMINDER and uncheck case sensitive & check entire scope & press Ok

By this time a new page will create for JE SHORTRAR

Now double click and rename JE SHORTRAR to JMP SHORTRAR then click with file with NOP assemble, click on the edited line & copy to executable

All modification and Copy all

New file will come, save the file (Save file to desktop for easy access)

Resource Hacker

Resource Hacker also known as ResHacker or ResHack is a free resource extraction utility and resource compiler for Windows developed by Angus Johnson. It can be used to add, modify or replace most resources within Windows binaries including strings, images, dialogs, menus, Version Info and Manifest resources.

Download Resource Hacker & install

Go to file menu & choose the file you saved recently in the Desktop

Go to about us & change trail to full version/registered then click on compile script.

Visit OllyDbg and Resource Hacker website if you want to learn more.