OT - Reverse engineer a .dll & .exe

[Baron Grazic]

Question that I thought some of the members here might know about.
A programmer here created an application and has since left, deleting all his data and code for creating the application, and conveniently not leaving a backup.
We now need to modify 1 thing in the code?
Does anyone know how to reverse engineer a .dll & .exe file that was created using a VB developer tool?
Thanks.
Baron Grazic

[narf poit chez BOOM]

I think that's illegal.

[capnq]

I doubt that it's illegal for a company to decompile code that its employees/contractors custom wrote for it.

Still, it's an argument in favor of using Open Source applications whenever possible.

[Atrocities]

I remember when one of my former companies top programmers became so dissolutioned with the company that he simply walked in the middle of a high priority project and since he was senior programmer on the project he was the only one who knew the details of the program. Since the company had already invested several million into the project and didn't want to start over so they had to make arrangements to have him come back to work for them to finish the project. They paid him six times his wage as a consultant for his expertise. His contract gave him total control and he had more authority than his former boss and that alone made his day.

Good luck with the reverse engineering thing. It didn't work out well for my former company but I do hope it works out for yours.

[aegisx]

It is not illegal is the company owns it.

Reverse Engineering take some time to get good at, but check out IDA Pro. They have a free demo, but if your company is serious about it, they should buy it.

You should know what your getting into though...

There are not really any good tools to reverse it to source code that can compile. You may be able to make a binary change to the dll/exe depending on the change (i.e. byte for byte). IDA pro will not convert it to source code, it will just show you the assembly,objects etc.

[Aiken]

Disassembler is a little help when you're REing VB p-code.
Good decompiler might help a bit more: VBD.

[Ed Kolis]

VB? If it's VB.NET (not VB6 or earlier), then the code is only compiled into "MSIL" which is not really machine language, and it's actually possible (IIRC) to get meaningful source code out of it, unless it's been run through an obfuscator. You won't get the comments, of course, and you probably won't get the right names for the variables and such, but you will get real honest-to-God source code that you can mess with. Just Google ".net decompiler" for options. I've never actually used any of these tools before so I'm not sure how well they work, but I'm pretty sure there are even free tools to do this at a very basic level.
Of course if it's not .NET then none of what I said applies, but it's worth a try... worst you can do is get some error saying "this is not a .NET executable" or something!

[Dan_]

You can use Reflector to decompile .net assemblies.