User Account Control
UAC or User Account Control ( UAC) is a technology and security infrastructure that is used in the Windows operating system since Windows Vista. Is to facilitate the protection of the system for the default user.
Risk and meaning full access rights
Versions of Windows that are earlier than Windows NT or not it descended ( for example, Windows 3.1, Windows 95, 98, and ME), were single-user systems, where the user had full control of the system. Windows systems in the NT line, however, are multi-user systems, so that different user roles and rights can be assigned.
For Windows XP ( up to 5) get created user account administrator rights during installation. As a result, many equipped with Windows XP computers are always operated with full administrator rights. Thus, any software, even malicious software, started with administrator rights, so that they have full access to the system.
In many legacy applications and some current applications limited user rights were not considered, although this Microsoft stipulated as a minimum requirement in the "Designed for Windows " directives with Windows 95 for the first time published. Installs or start one such software with limited rights, errors occur or the software is not working properly. Thus, it is often common practice to equip normal user with administrator privileges. Would the Windows first-time users be therefore standard with limited rights, such programs be rendered unusable if the user has not extensively with the Windows user structure.
Solution
UAC has been introduced in order to increase the security of the systems. This also applies to the display of web pages, which are a potential security risk.
For all Windows versions from Windows Vista to activities which could endanger the safety or stability of the operating system by an administrator to be confirmed ( by entering the appropriate user name and password ). If the user is already logged in as administrator, a selection dialog appears, so that the action can be prevented. Starting with Windows 7, the UAC can also be set in different security levels.
Criticism
It is complained that UAC various workflows slows the computer, especially the first time setting up a Windows Vista operating system. However, it is possible to turn off the UAC Notifications to install, for example, safe software without further inquiries can. Can then be re-enabled UAC.
Also there is the fear that a permanently switched on UAC seduces the user to confirm each dialogue blind. This behavior could be promoted by the low information content of the UAC message. This would cause the system to absurdity.
Even Microsoft itself is the partial refusal, the UAC by the user aware. Thus, the company formulated the statement " Windows 7 UAC is now less disruptive ," which Microsoft admits obstructing the user.
Operation
If a user logs on without administrator rights on Windows Vista / 7, so a new session with the basic rights is established. Thus can be made of this session from any changes that affect the entire system. Reports on the other hand, a user in the Administrators group, then a new session with two rights contexts is established. A rights -based context with restricted rights and a second with the extended administrator rights.
User applications, such as Windows Explorer, all starting with limited rights so that there is effectively a restricted environment under an administrator account. Now an application requires elevated privileges, they will be requested through the UAC mechanism. A confirmation dialog is displayed, and if the desired action is confirmed by the user, the session continued with unrestricted rights. In the Secure Desktop mode, the user data (username and password ) can be queried by UAC by the fact that the entire screen is darkened except for the authorization dialog and disabled. This is to protect against abuse (see spoofing ).
Not all common tasks, such as changing the time zone in Windows Vista require Administrator rights.
UAC also offers a file and registry virtualization, so not prepared for that purpose programs are still run with standard rights. File accesses of these programs on the appropriate system folder (eg C: \ Program Files \ ) are redirected to C: \ Users \ % USERNAME % \ AppData \ Local \ VirtualStore \. Accesses to the registry of non-UAC -prepared programs are redirected to HKEY_CURRENT_USER \ Software \ Classes \ VirtualStore. Once in the Windows Control Panel, UAC is disabled, the programs would respond with error messages or malfunctions, since the accesses to the locked areas of the system can not be redirected.
In the Windows Task Manager column UAC virtualization can be displayed. There, the status regarding the UAC virtualization of running programs or processes can be read. Program developers, the programs should be characterized by the integration of the below XML file.
In a command prompt that is running with elevated privileges, the prefix "Administrator" is prefixed to the title, so that is easily distinguishable, which prompt running with elevated privileges.
UAC with, it is possible to determine that:
- Administrators must enter their password again (to increase security).
- The user Ctrl Alt Del to enter as part of the authentication process ( to increase security ).
- Is completely off the Admin Approval Mode ( UAC appears when the administrator).
Adaptation of the UAC
Requesting elevated privileges
A program may require extended rights in various ways. One possibility is that a portion requestedPrivileges is added to an XML document, the manifest. This manifesto is later incorporated into the application. Usually specifies a manifest dependencies, visual styles and other characteristics of the program.
Security section in a manifest document:
To start a new process with elevated privileges from a. NET application, the command " runas " can be used.
An example in C #:
System.Diagnostics.Process proc = new System.Diagnostics.Process (); proc.StartInfo.FileName = "C: \ \ windows \ \ system32 \ \ notepad.exe "; proc.StartInfo.Verb = " runas "; / / Elevate the application proc.Start (); In COM applications can " runas " command is added to the call ShellExecute ().
:: ShellExecute (0, " runas ", "C: \ \ Windows \ \ Notepad.exe ", 0, 0, SW_SHOWNORMAL ); Disable UAC for certain applications
For selected applications, the User Account Control Compatibility Mode can be disabled or for legacy applications are permanently fixed.