This doesn't work anymore. FiveM fixed this issue 17-02-2022.
.NET Framework 4.7.2 +
• Set Borderless Windowed Mode.
• Open my 'FiveM-Crasher.exe' binary only when you're ALREADY IN GAME.
• You CAN'T enter interiors after activate my CRASHER once, otherwise, your account may become permanently useless on the server
• You can deactivate Launcher music by deleting the .mp3 file inside Launcher folder, or deleting [AUDIO] section inside 'config.ini'.
I made this just for DEMONSTRATION, without the purpose of ruining FiveM servers completely.
Remembering, this is classified as Denial Of Service, also provided for your country law as an Internet crime.
You need to reference my edited MaterialSkins.dll that I uploaded in the source folder.
You need to provide two images inside /Launcher folder in the same location as de Binary Compiled (SplashScreen.png and Loading.png).