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In computer security, 'logging' (or 'signing') 'in and out' is the process by which individual access to a computer system is controlled by identification of the user in order to obtain credentials to permit access. It is an integral part of computer security. A user can log in to a system to obtain access, and then log out when the access is no longer needed. Note that the term ''log in'' (a verb) is two words, while ''login'' (a noun referring to the procedure, credentials, or form used) is one word; the same applies to ''log out'' and ''logout''.

Contents

Logging in

Logging out

See also

Logging in

To ''log in'' (also: to ''log on'', ''sign in'', or ''sign on'') is to identify oneself to the system in order to obtain access. The concept derives from the action of ''clocking in'' on arrival at a factory, where a worker would stamp a timesheet or card upon their arrival. Its usage in computing derives from IBM parlance.
The primary use of a computer login procedure is to authenticate the identity of any computer user (or computer software on this or a different computer) attempting to access the computer's services. The login procedure can also provide an audit trail of the use of the system.
To log in to a system usually requires:

★ a user name, a unique sequence of characters the user chooses to represent himself or herself with. A user name can be the user's real name, but is more often a short nickname or screen name.

★ a password, another sequence of characters which provides the user with a ''key'' to the system and is kept secret from others.

Logging out

To ''log out'' (also: to ''log off'', ''sign out'', or ''sign off'') is to close off one's access to a computer system after previously having logged in.
Logging out may be done explicitly by the user performing some action, such as entering the appropriate command, or clicking a website link labeled as such. It can also be done implicitly, such as by powering the machine off, closing a web browser window, leaving a website, or not refreshing a webpage within a defined period.
In the case of web sites that use cookies to track sessions, when the user logs out, session-only cookies from that site will usually be deleted from the user's computer. In addition, the server invalidates any associations with the session, making any session-handle in the user's cookie store useless. This features comes in handy if the user is using a public computer.
Logging out of a computer when leaving it is a common security practice, preventing unauthorized users from tampering with it. Many people choose to have a password-protected screensaver to kick in after some time of inactivity, requiring the user to log in again to regain access.

See also

★ Computer security

★ Account

★ Password

★ Password policy

★ Login spoofing

★ Login session

★ OpenID

★ /var/log/wtmp