OllyDbg is the most wanted classical low level reverse engineering 32-bit disassembler, analyzing, and runtime MASM debugger tool.
Its works on Microsoft Windows OS, and can debugging and analysis the windows binary and pre-compiled files ie ( .exe, .dll extension files etc…).
And that is exactly what makes it a very useful and practical solution when modifying, debugging, and hacking complied bin files. so in cases where the source is unavailable or not.
The classic Dasm (disassembler) and Debuggers OllyDbg is still useful specially for Embed Systems Engineering processing and for C Programmers.
While installing you can safely ignore any virus alerts, because its of course a false positive case :), due to the nature of the type of this software.
OllyDbg can be attached to currently running and live-in memory programs. also, it's fully Unicode, and a multi-thread app-supported debugger.
OllyDbg can do code analysis with tracing memory registers in runtime, recognizes procedures so can follow jumps, loops, calls, and strings etc…
OllyDbg can search whole file or runtime allocated memory of a file, and so debugging, modify procedures in Hexa or MASM format, and set breakpoints. all on the fly.
OllyDbg can also understating Debugging information in Borland format. and disassembler, both MASM and IDEAL formats, and more…
In the most classic example of reverse engineering a bin file, you can specify the MASM bad boy jump code and modify it to do nothing (9090) in Hexa so It can be an alternative to W32dasm and Hexa editors apps together.
What About X86_64 Debugger
Fortunately you can use the opensource x64dbg Debugger for windows.
Download from source:OllyDbg FullPack