I am currently developing a social networking site using RoR that uses the attachment_fu plugin to handle image uploads. I also want to enable users to upload photoshop files, but am worried about security vulnerabilities because I want other users to be able to download these photoshop files. What is to stop someone from uploading a malicious file (i.e. virus) just by changing the extension? I don't want someone downloading a file with a virus on it from my site. Is there any way to screen files for viruses when they are uploaded in RoR? Any thoughts? Thanks.