Material Emancipation Grill

Wikipedia has experimented with systems in which edits to some articles, especially those of living people, are delayed until it can be reviewed and determined that they are not vandalism, and in some cases, that a source to verify accuracy is provided. This is in an effort to prevent inaccurate and potentially damaging information about living people from appearing on the site.

ClueBot NG
The most well-known "bot" that fights vandalism is ClueBot NG. The bot was created by Wikipedia users Christopher Breneman and Cobi Carter in 2010 (succeeding the original ClueBot created in 2007; NG stands for Next Generation) and uses machine learning and Bayesian statistics to determine if an edit is vandalism.

While the bot has been effective in helping keep Wikipedia clean, some claim the bot is hostile to new users by not being able to apply a human brain's knowledge to the edit, and leaving impersonal.

Blacklisting
The MediaWiki title blacklist extension prevents page move vandalism and creation vandalism by using regular expressions to identify bad titles. Titles on the blacklist can only be created by or moved to by administrators. Pages that are also created repeatedly can be protected to prevent vandals from recreating bad pages.

In addition to the title blacklist, the spam blacklist prevents external link spamming, a form of vandalism. New/unregistered users who want to add external links are required to answer a CAPTCHA.

The "bad image list" prevents images that could be used to vandalize pages from being inserted, such as images with sexual content. Images on the list can be added only to pages where the use of the image is explicitly allowed.

The entirety of the MediaWiki namespace, the main page, and high-risk templates are protected to prevent high server load and sudden interface changes.

The edit filter can also prevent vandalism by disallowing the bad edit altogether, or by allowing only autoconfirmed users or administrators to perform the edit.

Seigenthaler incident


In May 2005, a user edited the biographical article about John Seigenthaler, Sr. so that it contained several false and defamatory statements. The inaccurate claims went unnoticed between May and September 2005, after which they were discovered by Victor S. Johnson, Jr., a friend of Seigenthaler. Wikipedia content is often mirrored at sites such as Answers.com, which means that incorrect information can be replicated alongside correct information through a number of websites. Such information can develop a misleading air of authority because of its presence at such sites: "Then [Seigenthaler's] son discovered that his father's hoax biography also appeared on two other sites, Reference.com and Answers.com, which took direct feeds from Wikipedia. It was out there for four months before Seigenthaler realized and got the Wikipedia entry replaced with a more reliable account. The lies remained for another three weeks on the mirror sites downstream."

Stephen Colbert
Comedian Stephen Colbert made repeated references to Wikipedia on his TV show The Colbert Report, frequently suggesting on-air that his viewers vandalize selected pages. These instances include the following:
 * On a 2006 episode of his show, Colbert suggested viewers vandalize the article "Elephant". This resulted in his Wikipedia account named "Stephencolbert" being blocked from editing, as well as many elephant-related articles being protected.
 * On 7 August 2012, Colbert suggested that his viewers go to pages for possible 2012 U.S. Republican vice-presidential candidates, such as the Tim Pawlenty and Rob Portman articles, and edit them many times. This was in response to a Fox News hypothesis that mass editing of the Sarah Palin page the day before she was announced as John McCain's running mate could help predict who would be chosen as Mitt Romney's running mate in the 2012 election. After Colbert's request and his viewers' subsequent actions, all these articles were put under by Wikipedia administrators, with editing restricted to established users.

Hillsborough disaster vandalism
In April 2014, the Liverpool Echo reported that computers on an intranet used by the British government had been used to post offensive remarks about the Hillsborough disaster on Wikipedia pages relating to the subject. The government announced that it would launch an inquiry into the reports. Following the allegations, The Daily Telegraph reported that government computers appeared to have been used to vandalize a number of other articles, often adding insulting remarks to biographical articles, and in one case falsely reporting a death.

Political vandalism
Politicians are a common target of vandalism on Wikipedia. The article on Donald Trump was replaced with a single sentence critical of him in July 2015,  and in November 2018, the lead picture on the page was replaced with an image of a penis, causing Apple's virtual assistant Siri to briefly include this image in answers to queries about the subject. Both Hillary and Bill Clinton's Wikipedia pages were vandalized in October 2016 by a member of the Internet trolling group Gay Nigger Association of America adding pornographic images to their articles. That same month, New York Assembly candidate Jim Tedisco's Wikipedia page was modified to say that he had "never been part of the majority", and "is considered by many to be a total failure". Tedisco expressed dismay at the changes to his page. On 24 July 2018, Utah senator Orrin Hatch posted humorous tweets after Google claimed that he had died on 11 September 2017, with the error being traced back to an edit to his Wikipedia article. Similarly, vandalism of the California Republican Party's Wikipedia page caused Google's information bar to list Nazism as one of the party's primary ideologies.

The week of 29 January 2017 saw various acts of Wikipedia vandalism that attracted media attention. White House Press Secretary Sean Spicer's Wikipedia page was vandalized and his picture replaced with that of Baghdad Bob, Dana J. Boente's page description was edited to read that he was "the newest sock puppet for the Trump Administration", and Paul Ryan's picture was added to a list of invertebrates, with the edit summary stating that he was added due to his lack of a spine.

On 27 September 2018, the personal information of United States senators Lindsey Graham, Mike Lee, and Orrin Hatch were added to their respective Wikipedia articles during the hearing of Supreme Court Nominee Judge Brett Kavanaugh. The information included their home addresses and phone numbers, and originated from the network located from within the United States House of Representatives. The edits were removed from Wikipedia and hidden from public view shortly afterwards. These edits were captured and automatically posted publicly to Twitter by an automated account. Twitter shortly removed the posts and suspended the account in response to the incident. An internal police investigation located the person who made the edits, and 27-year-old Jackson A. Cosko (a staffer for Congress paid by an outside institution) was arrested and charged with multiple felony crimes relating to the incident. Cosko was sentenced in 2019 to four years in prison after pleading guilty to five felonies.

Miscellaneous

 * A vandal called "Willy on Wheels" moved thousands of articles so that their titles ended with "on wheels".
 * In 2006, Rolling Stone printed a story about Halle Berry based on false information from Wikipedia, which had arisen from an act of Wikipedia vandalism.
 * In February 2007, professional golfer Fuzzy Zoeller sued a Miami company whose IP-based edits to the Wikipedia site included negative information about him.
 * In August 2007, local media from the Netherlands reported that several IP addresses from Nederlandse Publieke Omroep had been blocked from Wikipedia for adding "false and defamatory" information to pages. A similar incident occurred with the Minister of the Interior in France in January 2016.
 * In May 2012, media critic Anita Sarkeesian created a Kickstarter project, intending to raise money to make a series of videos exploring sexism in digital gaming culture. The idea evoked a hostile response, which included repeated vandalism of Sarkeesian's Wikipedia article with pornographic imagery, defamatory statements, and threats of sexual violence. More than 12 IP addresses from unregistered editors contributed to the ongoing vandalism campaign before editing privileges were revoked for the page.
 * In May 2012, webcomic and humor website The Oatmeal published a comic in which it is suggested that Thomas Edison should be added as an example to the disambiguation page "". After having Edison added and removed several times, the page was extended-confirmed protected.
 * In November 2012, the Leveson report – published in the UK by Lord Justice Leveson – incorrectly listed a "Brett Straub" as one of the founders of The Independent newspaper. The name originated from one of the several erroneous edits by one of Straub's friends as a prank to Wikipedia by falsely including his name in several articles across the site. The name's inclusion in the report suggested that part of the report relating to that newspaper had been cut and pasted from Wikipedia without a proper check of the sources. The Straub issue was also humorously referenced in broadcasts of BBC entertainment current affairs TV program Have I Got News for You (and extended edition Have I Got a Bit More News for You),  with The Economist also making passing comment on the issue: "The Leveson report... Parts of it are a scissors-and-paste job culled from Wikipedia."
 * In April 2015, The Washington Post reported on an experiment by "Gregory Kohs, a former editor, and prominent Wikipedia critic": "Kohs wrapped up an experiment in which he inserted outlandish errors into 31 articles and tracked whether editors ever found them. After more than two months, half of his hoaxes still had not been found – and those included errors on high-profile pages, like "" and "". (By his estimate, more than 100,000 people have now seen the claim that volcanic rock produced by the human body causes inflammation pain.)"
 * In August 2016, a sentence was added to saying that he "Died at the hands of Michael Phelps, being literally blown out of the water by the greatest American since Abraham Lincoln" after Phelps won the gold medal for 200-meter butterfly at the 2016 Summer Olympics. This particular instance of Wikipedia vandalism attracted moderate media attention.
 * On 25 April 2018, various pages related to American video game director Todd Howard were vandalized after a post went viral on Tumblr stating that his page would no longer be semi-protected as of said date. Although Howard's page had its protection extended, a massive raid campaign vandalized many related pages. These included "" (the most popular game he worked on), "" (his hometown), and "" (after a Wikipedia administrator who reversed the vandalism).
 * On 16 August 2021, a template that was transcluded onto approximately 53,000 pages was replaced with a swastika. The vandalism was reverted five minutes later.