Most private servers operate on version 3.3.5a (Build 12340). This specific patch is favored for several reasons:
Never download an executable file ( .exe ) from a random forum post. Only download from established, trusted private server communities or verified archival projects. Wow 3.3 5a Download Full Client
This build is highly optimized and compatible with a wide range of custom launchers and addons. Most private servers operate on version 3