Virus on site....
 

http://i30.tinypic.com/15nne68.jpg

I apparently got some viruses on my site. This can not be related to custom mods since I haven't installed any for ages and this recently started to happen.

Every 12 hours or so my index get re-written. The source code says:
Code:
index.php" width=193 height=159 style="visibility: hidden">
WHAT I think I need help with is what folders I shoudl change permission on. Some time ago I gave access to all my folders on my forum folder for some stupid reason. Could soembody pease tell me what files/folders I should change permissions too and what I should change them too?