permissions

Great tips on protecting file uploads via PHP, discusses MIME server-side validation, as well file handling with suhosin and mod_security. Some info, is basic, but it covers more advanced topics like chroot and partition permissions.

Normally, when a program runs under Linux, it inherits the permissions of the user who is running it, thus if I run a program under my account, the program runs with the same permissions that I would have if that program were me. Thus, if I cannot open a certain file, the program I am running also cannot open the file in question. If I set the SUID or SGID bit for a file, this causes any persons or processes that run the file to have access to system resources as though they are the owner of the file.