You can report obvious and persistent vandals at Wikipedia:Administrator intervention against vandalism. Before posting 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. Your block request is unlikely to be acted upon unless you follow these steps. Cases that are not simple vandalism can be reported at WP:AN/I. 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.

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