Operating system variations
Unix-like and otherwise POSIX-compliant systems, including Linux-based systems and all Mac OS X versions, have a simple system for managing individual file permissions, which in this article are called "traditional Unix permissions". Most of these systems also support some kind of access control lists, either proprietary (old HP-UX ACLs, for example), or POSIX.1e ACLs, based on an early POSIX draft that was abandoned, or NFSv4 ACLs, which are part of the NFSv4 standard.
Microsoft and IBM DOS variants (including MS-DOS, PC DOS, Windows 95, Windows 98, Windows 98 SE, and Windows Me) do not have permissions, only file attributes. There is a read-only attribute (R), which can be set or unset on a file by any user or program, and therefore does not prevent him/her from changing/deleting the file. There is no permission in these systems which would prevent a user from reading a file.
References:
Web Application Security, Hacking, Windows Security, Cross Site Scripting, SQL Injection, XSS, XXE, XML
