Vandalism is any addition, removal, or change of content in a deliberate attempt to compromise the integrity of Wikipedia. Examples of typical vandalism are adding irrelevant obscenities and crude humor to a page, illegitimately blanking pages, and inserting patent nonsense into a page. Vandalism is prohibited.
Even if misguided, willfully against consensus, or disruptive, any good-faith effort to improve the encyclopedia is not vandalism. Edit warring over content is not vandalism. Careful consideration may be required to differentiate between edits that are beneficial, detrimental but well-intentioned, and vandalizing.
Upon their discovery, revert clearly vandalizing edits. Then warn the vandalizing editor. Notify administrators of vandalizing users who persist despite warnings, and administrators should intervene to protect content and prevent further disruption by blocking such users from editing. When warranted, accounts whose main or only use is obvious vandalism or other forbidden activity may be blocked even without warning.