Administrators can protect and unprotect pages to prevent articles from being edited or images from being overwritten. There are two levels of protection above the standard unprotected state of a page. A page can be fully protected so that only administrators can edit them, or semi-protected so that only autoconfirmed users and above can modify them.
Full protection is generally reserved for policy pages and other administrative efforts; However, in rare cases, mainspace articles may be temporarily (or even permanently) protected to combat extreme cases of vandalism or edit warring. Articles that receive high levels of traffic are preferably placed under semi-protected status to prevent newly registered users from tampering with sensitive information.
Common reasons for protection
Maintaining the integrity of the user interface, such as that of the Main Page and favicon.
Maintaining the integrity of important policy pages or copyright and license information.
All MediaWiki system pages are permanently protected by default.
Protecting pages that are particularly suspectible to misinformation or speculation, such as upcoming projects.
Temporary protections may be used to diffuse edit wars.