On Wikipedia, vandalism is editing the project in an intentionally disruptive or malicious manner. Vandalism includes any addition, removal, or modification that is intentionally humorous, nonsensical, a hoax, offensive, libelous or degrading in any way.
Throughout its history, Wikipedia has struggled to maintain a balance between allowing the freedom of open editing and protecting the accuracy of its information when false information can be potentially damaging to its subjects. Vandalism is easy to commit on Wikipedia because anyone can edit the site, with the exception of protected pages (which, depending on the level of protection, can only be edited by users with certain privileges). Certain Wikipedia bots are capable of detecting and removing vandalism faster than any human editor could.
It is not a criminal act to vandalize Wikipedia. However, it is against the site's terms of use to vandalize or otherwise cause disruption. Vandals are blocked from editing, and may also be further banned according to the terms of use. Vandalism can be committed by either guest editors (IP addresses) or those with registered accounts. To combat inappropriate user edits, Wikipedia has instated a protection policy, serving as a user-privilege merit system. For example, a semi-protected or fully protected page can be edited only by accounts that meet certain account age and activity thresholds or administrators respectively. Frequent targets of vandalism include articles on trending and controversial topics, celebrities, and current events. In some cases, people have been falsely reported as having died. This has notably happened to United States Senators Ted Kennedy and Robert Byrd, and American rapper Kanye West.
Prevention
There are various measures taken by Wikipedia to prevent or reduce the amount of vandalism. These include: Using Wikipedia's history functionality, which retains all prior versions of an article, restoring the article to the last version before the vandalism occurred; this is called reverting vandalism. The majority of vandalism on Wikipedia is reverted quickly. There are various ways in which the vandalism gets detected so it can be reverted: Bots: In some cases, the vandalism is automatically detected and reverted by a Wikipedia bot. The vandal is always warned with no human intervention. Recent changes patrol: Wikipedia has a special page that lists all the most recent changes. Some editors will monitor these changes for possible vandalism. Watchlists: Any registered user can watch a page that they have created or edited or that they otherwise have an interest in. This functionality also enables users to monitor a page for vandalism. Incidental discovery: Any reader who comes across vandalism by chance can revert it. In 2008, it was reported that the rarity of such incidental discovery indicated the efficacy of the other methods of vandalism removal. Protecting articles so only established users, or in some cases, only administrators can edit them. Semi-protected articles are those that can be edited only by those with an account that is autoconfirmed (at least four days old with at least ten edits). Fully protected articles are those that can be edited only by administrators. Protection is generally instituted after one or more editors make a request on a special page for that purpose. An administrator familiar with the protection guidelines chooses whether or not to fulfill this request based on the guidelines. Blocking and banning those who have repeatedly committed acts of vandalism from editing for a period of time or in some cases, indefinitely. Vandals are not blocked as an act of punishmentthe purpose of the block is simply to prevent further damage. The "abuse filter" extension, which uses regular expressions to detect common vandalism terms. Editors are generally warned before being blocked. Wikipedia employs a 5-stage warning process leading up to a block. This includes: The first warning "assumes good faith" and takes a relaxed approach to the user. (in some cases, this level can be skipped if the editor assumes the user is acting in bad faith). The second warning does not assume any faith and is an actual warning (in some cases, this level may also be skipped). The third warning assumes bad faith and is the first to warn the user that continued vandalism may result in a block. The fourth warning is a final warning, stating that any future acts of vandalism will result in a block. After this, other users may place additional warnings, though only administrators can carry out the block.