[ancieque]

I remember installing a metamod plugin to my cs 1.5 Server that added server side fog of war iirc. But i could be mixing things up.

[shaokind]

SMAC certainly predates Valve’s official implementation, wouldn’t be surprising if something else also did it.

[CodeArtisan]

Probably CSGuard/HLGuard. It had a popular wallhack-block feature that was using a lot of CPU.