In computing, privilege is defined as the delegation of authority to perform security-relevant functions on a computer system. A privilege allows a user to perform an action with security consequences. Examples of various privileges include the ability to create a new user, install software, or change kernel functions.
Users who have been delegated extra levels of control are called privileged. Users who lack most privileges are defined as unprivileged, regular, or normal users.
Theory
Privileges can either be automatic, granted, or applied for.
An automatic privilege exists when there is no requirement to have permission to perform an action. For example, on systems where people are required to log into a system to use it, logging out will not require a privilege. Systems that do not implement file protection - such as
MS-DOS
MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few ope ...
- essentially give unlimited privilege to perform any action on a file.
A granted privilege exists as a result of presenting some credential to the privilege granting authority. This is usually accomplished by logging on to a system with a
username
A user is a person who utilizes a computer or network service.
A user often has a user account and is identified to the system by a username (or user name). Other terms for username include login name, screenname (or screen name), accoun ...
and
password
A password, sometimes called a passcode (for example in Apple devices), is secret data, typically a string of characters, usually used to confirm a user's identity. Traditionally, passwords were expected to be memorized, but the large number of ...
, and if the username and password supplied are correct, the user is granted additional privileges.
A privilege is applied for by either an executed program issuing a request for advanced privileges, or by running some program to apply for the additional privileges. An example of a user applying for additional privileges is provided by the
sudo
sudo ( or ) is a program for Unix-like computer operating systems that enables users to run programs with the security privileges of another user, by default the superuser. It originally stood for "superuser do", as that was all it did, and it i ...
command to run a command as superuser (''root'') user, or by the Kerberos authentication system.
Modern processor architectures have multiple
CPU modes
CPU modes (also called ''processor modes,'' ''CPU states,'' ''CPU privilege levels'' and other names) are operating modes for the central processing unit of some computer architectures that place restrictions on the type and scope of operations t ...
that allows the OS to run at different privilege levels. Some processors have two levels (such as ''user'' and ''supervisor'');
i386
The Intel 386, originally released as 80386 and later renamed i386, is a 32-bit microprocessor introduced in 1985. The first versions had 275,000 transistorsC, which use pointer arithmetic or do not check array bounds automatically.
Unix
On
Unix-like
A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-li ...
systems, the
superuser
In computing, the superuser is a special user account used for system administration. Depending on the operating system (OS), the actual name of this account might be root, administrator, admin or supervisor. In some cases, the actual name of t ...
(commonly known as 'root') owns all the privileges. Ordinary users are granted only enough permissions to accomplish their most common tasks. UNIX systems have built-in security features. Most users cannot set up a new user account nor do other administrative procedures. The user “root” is a special user, something called super-user, which can do anything at all on the system. This high degree power is necessary to fully administer a UNIX system, but it also allows its user to make a mistake and cause system problems.
Unprivileged users usually cannot:
*Adjust
kernel
Kernel may refer to:
Computing
* Kernel (operating system), the central component of most operating systems
* Kernel (image processing), a matrix used for image convolution
* Compute kernel, in GPGPU programming
* Kernel method, in machine learnin ...
options;
*modify system files, or files of other users.
*change the ownership of any files;
*change the runlevel (on systems with
System V
Unix System V (pronounced: "System Five") is one of the first commercial versions of the Unix operating system. It was originally developed by AT&T and first released in 1983. Four major versions of System V were released, numbered 1, 2, 3, an ...
-style initialization);
*change the file mode of any files;
*adjust ulimits or
disk quota
A disk quota is a limit set by a system administrator that restricts certain aspects of file system usage on modern operating systems. The function of using disk quotas is to allocate limited disk space in a reasonable way.
Types of quotas
There ...
s;
*start, stop and remove daemons;
*signal processes of other users;
*create device nodes;
*create or remove users or groups;
*mount or unmount volumes (although it is becoming common to allow regular users to mount and unmount removable media, such as
compact disc
The compact disc (CD) is a Digital media, digital optical disc data storage format that was co-developed by Philips and Sony to store and play digital audio recordings. In August 1982, the first compact disc was manufactured. It was then rele ...
s - this is typically accomplished via
FUSE
Fuse or FUSE may refer to:
Devices
* Fuse (electrical), a device used in electrical systems to protect against excessive current
** Fuse (automotive), a class of fuses for vehicles
* Fuse (hydraulic), a device used in hydraulic systems to protect ...
);
*execute the contents of any sbin/ directory (although it is becoming common to simply restrict the behavior of such programs when executed by regular users);
* bind ports below 1024.
Windows NT
On
Windows NT
Windows NT is a proprietary graphical operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs.
Time-sharing operating systems sc ...
-based systems, privileges are delegated in varying degrees. These delegations can be defined using the local security policy manager (secpol.msc). The following is an abbreviated list of the default assignments:
*'NT AUTHORITY\System' is the closest equivalent to the Superuser on Unix-like systems. It has many of the privileges of a classic Unix superuser (such as being a trustee on every file created);
*'Administrator' is one of the closest equivalents to the superuser (root) on Unix-like systems. However, this user cannot override as many of the operating system's protections as the superuser can;
*members of the 'Administrators' group have privileges almost equal to 'Administrator';
*members of the 'Power Users' group have the ability to install programs and
backup
In information technology, a backup, or data backup is a copy of computer data taken and stored elsewhere so that it may be used to restore the original after a data loss event. The verb form, referring to the process of doing so, is "back up", w ...
the system.
*members of the 'Users' group are the equivalent to unprivileged users on Unix-like systems.
Windows defines a number of administrative privileges that can be assigned individually to users and/or groups. An account (user) holds only the privileges granted to it, either directly or indirectly through group memberships. Upon installation a number of groups and accounts are created and privileges are granted to them. However, these grants can be changed at a later time or though a
group policy
Group Policy is a feature of the Microsoft Windows NT family of operating systems (including Windows 7, Windows 8.1, Windows 10, Windows 11, and Windows Server 2003+) that controls the working environment of user accounts and computer accounts. G ...
. Unlike Linux, no privileges are implicitly or permanently granted to a specific account.
Some administrative privileges (e.g. taking ownership of or restoring arbitrary files) are so powerful that if used with malicious intent they could allow the entire system to be compromised. With
user account control
User Account Control (UAC) is a mandatory access control enforcement feature introduced with Microsoft's Windows Vista and Windows Server 2008 operating systems, with a more relaxed
(on by default since Windows Vista) Windows will strip the user token of these privileges at login. Thus, if a user logs in with an account with broad system privileges, he/she will still not be ''running'' with these system privileges. Whenever the user wants to perform administrative actions requiring any of the system privileges he/she will have to do this from an ''elevated'' process. When launching an ''elevated'' process, the user is made aware that his/her administrative privileges are being asserted through a prompt requiring his/her consent. Not holding privileges until actually required is in keeping with the
principle of least privilege
In information security, computer science, and other fields, the principle of least privilege (PoLP), also known as the principle of minimal privilege (PoMP) or the principle of least authority (PoLA), requires that in a particular abstraction la ...
.
Elevated processes will run with the full privileges of the ''user'', not the full privileges of the ''system''. Even so, the privileges of the user may still be more than what is required for that particular process, thus not completely
least privilege
In information security, computer science, and other fields, the principle of least privilege (PoLP), also known as the principle of minimal privilege (PoMP) or the principle of least authority (PoLA), requires that in a particular abstraction la ...
.
The DOS-based Windows ME, Windows 98, Windows 95 and previous versions of non-NT Windows only operated on the FAT filesystem, did not support filesystem permissions and therefore privileges are effectively defeated on Windows NT-based systems that do not use the
NTFS
New Technology File System (NTFS) is a proprietary journaling file system developed by Microsoft. Starting with Windows NT 3.1, it is the default file system of the Windows NT family. It superseded File Allocation Table (FAT) as the preferred fil ...
file system.
Nomenclature
The names used in the Windows source code end in either "privilege" or "logonright". This has led to some confusion about what the full set of all these "rights" and "privileges" should be called.
Microsoft currently uses the term "user rights".
In the past some other terms have also been used by Microsoft, such as "privilege rights"
, "logon user rights"
and "nt-rights".
See also
*
File-system permissions
Most file systems include attributes of files and directories that control the ability of users to read, change, navigate, and execute the contents of the file system. In some cases, menu options or functions may be made visible or hidden dependin ...
*
Kernel (operating system)
The kernel is a computer program at the core of a computer's operating system and generally has complete control over everything in the system. It is the portion of the operating system code that is always resident in memory and facilitates in ...
*
Principle of least privilege
In information security, computer science, and other fields, the principle of least privilege (PoLP), also known as the principle of minimal privilege (PoMP) or the principle of least authority (PoLA), requires that in a particular abstraction la ...
*
Superuser
In computing, the superuser is a special user account used for system administration. Depending on the operating system (OS), the actual name of this account might be root, administrator, admin or supervisor. In some cases, the actual name of t ...
*
Privilege escalation
Privilege escalation is the act of exploiting a bug, a design flaw, or a configuration oversight in an operating system or software application to gain elevated access to resources that are normally protected from an application or user. The re ...