You can report obvious and persistent vandals at Wikipedia:Administrator intervention against vandalism (WP:AIV) to be blocked from further editing. Although blocks may be issued at any time, depending on circumstances, typically, before seeking a block there, a final warning in an escalating series should have been posted to the user's talk page (for example {{Uw-vandal4}}, {{Uw-spam4}} or {{Uw-speedy4}}), and the user must have vandalized within the last few hours, including after the final warning was given. Various warning templates can be found at Wikipedia:Template messages/User talk namespace (easily remembered by the shortcut WP:WARN). Your block request is unlikely to be acted upon unless you follow these steps. Cases that are not simple vandalism can be reported at Wikipedia:Administrators' noticeboard/Incidents. Of course, in conjunction with warning against and reporting vandalism, you have the ability, mandate and are encouraged to revert all instances of vandalism you find yourself.
This template should always be substituted (i.e., use {{subst:Report vandal}}). Any accidental transclusions will be automatically substituted by a bot.
