A tiny 5KB file is almost certainly a virus.
Unlike a .zip or .rar file, a FastFile is not meant to be opened manually. The game engine loads these files directly into memory (RAM) to stream assets like textures, models, sound effects, and scripting logic. Download Code-pre-gfx.ff
To sum up: 90% of the top Google results for this keyword lead to adware or trojans. Instead: A tiny 5KB file is almost certainly a virus
If you are playing the newer engine (IW 8.0), the file structure has changed slightly, but the principle remains. the file structure has changed slightly