file uploading and security

I did a search on the forum, but didn't find this issue addressed directly.

If I enable file updoading (even if I restrict to certain types of files), isn't their still a big security concern?  What if someone uploads a document with some insidious macro?

How can I protect myself against this?

I tried reading documentation for aspSmartUpload and AspSimpleUpload and get about the same thing.  A brief description of registry properties as they relate to their respective program. 

Thanks for any help.