Mentioned this in another topic already, but the current theory is that the large number of downloads over a short amount of time combined with the small filesize makes windows think that the zip is a virus. Both me and another have tried scanning the file with 2 separate antivirus, both of which read it as safe. The only things in the zip are the game's EXE and .pck file, both of which were created by the game engine, and uploaded directly.