I have a web server with several domains hosted on it and have some folders set to 777 to allow (usually shopping carts) to write text files and upload images etc.

I have been hacked and all folders set to 777 have had files written to them which caused shopping carts etc to malfunction.

If I set the permissions to less than 777 I am unable to write successfully. Some servers are able to set permissions lower than 777 (say 755) others are not. I beleive this may be related to the PHP user which is usually set to 'nobody'.

I am getting a new server (with Fedora Core Linux) - how can this be set up so that PHP scripts within a domain can write to folders set lower than 777?

I do not believe your site was cracked because the folders/files permissions. A more logical cause is a bug in your php scripts that allow the attacker gain a shell with the same previlegies the php user has.

Anyway, change the owner of folders and files to the same php user. chmod -R nobody:nobody /path/to/your/rootdocumentfolder and chmod -R go-rwx /path/to/your/rootdocumentfolder.

good luck next time,

And if you don't want/can't set the files to be owned by the PHP user, then set the 'group' permissions to 7 and make sure that the PHP user is a member of the same group that owns the files.