Guest can download free with .rar file type extension
 

My forum have a trouble. Server allway shutdown. I find out that when I attachment some kind of file* guest can download the file with .rar extension. They needn't sign in while they download file from my site. They copy attachment file link to everywhere* and my server get trouble.

What can I do to set permissions with .rar files ?
You can see this link:
http://giaxaydung.vn/diendan/bo-lao-...93-2009-a.html
You can't download file .doc* .pdf* but you can download .rar file very easy* even you use accelator download software :(.
My server* CPU and MySQL always hang* die... Help me please. Thanks.