Avoiding viruses?

[L-28C <kixdemp@...>]

Hello everyone!

I'm making a game that uses Lua for most of its functions. I'm making it 
so that users can create their own levels/weapons/vehicles/modes in Lua, 
but what if they put viruses in the script?

What are some tips to avoid this problem? I can't disable file I/O 
because, for example, the maps might need to load text terrains. Maybe 
there's a way to only allow the script to load files from a certain 
directory?

Anything else I should know about this?

Thanks!