In 2004 I played an MMO game on a pirated server. The owner of the server somehow got a version of the server binary, and used a hex editor (!) to add new features to the binary over time.
It's the closest I've ever see to someone literally being one of the hackers from Matrix, literally staring at hexadecimal and changing chars one at a time
Presumably they were using a decompiler e.g. IDA Pro to know what characters to change in the hex editor? I've done that before to find offsets in the binary to NOP out some function calls.
I just remember when I cracked Space Empires III shareware as child. I didn't release the crack. Plus was a bit crappy, needing every time that I loaded the game, write a wrong serial so the check thought that was right serial code. I simple changed a few x86 opcodes to invert the check condition...
That's a level of dedication that I have never devoted to anything in my life.
That's energy that could change the world if harnessed correctly.
It did change the world - it made it better for players of the game.
That approach is also super useful if you're manually flashing an image onto some embedded thing (like an ECU, or other types of boot rom). Of course on many modern systems you'll have to get around the checksum guards, but there's typically all sorts of glitch hacks to do that.
Wasn't that WoW? I vaguely recall that a lot of the private servers worked off of a copied and / or decompiled version of their own server software for years, which is also why they never went further than the WotLK expansion. (the other part of that was people didn't want to, but that's another discussion)
AFAIK the WoW server code was never leaked. All private server code bases were developed by reverse engineering network traffic, game behaviour and client asset files.
E.g. the code for AzerothCore is fully available (and very easy to run on very low spec hardware)
https://github.com/azerothcore/azerothcore-wotlk
https://doomwiki.org/wiki/DeHackEd