Kunena attachment fails, directory owner issue perhaps?

Question

Just fixing my Joomla and Kunena forum after it was hacked :(

Now forum members can't upload attachments successfully, I've ttried changing permissions in the following:

public_html/media/kunena/attachments/666

666 being the user id and where the files are stored.

777 permissions works but isn't secure, 775 should work but doesn't, could this be an ownership issue? if so how would I change a few thousand of these to the correct owner and what should the owner be? Currently it's the cpanel username.

Any suggestions would be much appreciated.

Cheers

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UPDATE

A list of other problems that might spark an idea in the mind of your genius' out there.

1. Members can't upload / attach images to posts (I can't even do this with Super User)
2. Constant error in Admin: Warning: file_put_contents(/home/xxxxx/public_html/administrator/components/com_community/jomsocialupdate.ini) [function.file-put-contents]: failed to open stream: Permission denied in /home/xxxxx/public_html/libraries/joomla/filesystem/file.php on line 418
3. Attempted extension installation on fresh Joomla installation gives Failed to move error
4. Unable to update Joomla. Download of update package failed.

Answer 1

For Joomla/Kunena the recommended settings are 755 for directories and 644 for files

Source: http://docs.joomla.org/What_are_the_recommended_file_and_directory_permissions%3F