The old school way is to load recent changes and check the (diff) links. It can be filtered according to featured articles, good articles, living people, new editors' contribs, IPs' contribs and mobile contribs (as these are more prone to vandalism, see Help:Recent changes). Searching for articles by their namespace and specific tags (e.g. VisualEditor, possible BLP issue or vandalism, etc) can also be done. If they contain harmful edits, you revert to the previous version. However, the high volume of edits that occur each second makes this difficult to accomplish most of the time, and several tools have been created to simplify the process:
WP:WikiLoop Battlefield a web app for monitoring and labeling revisions. When labeled as "Should Revert" and is revert-able, it provides a quick link for user to go to Wikipedia to revert that specific revision. Direct link to the app: battlefield.wikiloop.org.
Vandal Fighter, the original anti-vandalism program, is a Java program that displays the Recent Changes feed from Wikipedia's IRC bots and allows filters to focus on certain types of changes (e.g. unregistered users). It also maintains a personal list of trusted users, watched articles, etc.
Lupin's Anti-Vandal Tool monitors the RSS feed and flags edits with common vandalism terms. It also has a live spellcheck feature. This tool works in monobook skin only.
WikiMonitor is a Windows program that enables users to monitor recent changes, their watchlist, users' contributions, and other feeds in real time as well as providing multiple tools to aid in semi-automated editing and reversion. It is compatible with all Wikimedia wikis.
WikiGuard is a Mac OS X program that monitors the IRC feed and attempts to approximate each edit's risk.
RC birds is a Java program that emits different bird sounds for the RC feed depending on the user.
The IRC Bot, pgkbot, by Pgk, runs on the IRC channels below.
IRC Bots reporting at the #cvn-wp-enconnect channel on the freenode network list suspected vandalism edits (for example: blankings, edits made by blacklisted users, etc.) (Use this link to open the IRC channel on a web browser.)
WikiAlerter, a Windows program for patrolling new pages, and deleting/tagging them. Designed primarily for CSD, but supports AfD and ProD. Currently in beta, but there is a release.
Huggle is a fast diff browser which parses edits from users and sorts them by predicted level of vandalism. Once identified, malicious edits can be reverted in the click of a button. Due to the fast-paced nature of the program, users on the English Wikipedia must have the rollback permission to use it; however, this is not a requirement on other wikis.
WatchlistBot is an XMPP bot that sends messages in realtime when articles are modified. Users with a Jabber account can subscribe to the bot and watch both articles and users.
WikipediaVision is a web-based world map visualization of unregistered edits to the English (and the German, French, Spanish, Swedish) Wikipedia, almost the same time as they happen.
STiki is a Java program that consists of (1) a server-side component that listens to the RC feed and scores edits in a machine-learning fashion (using 12+ features, many of which are not language-based) -- and (2) A client-side Java GUI application that presents likely vandalism found on the server-side to human users for inspection/reversion. Using STiki without rollback requires either approval from the developer or 1000 article-space edits. It can revert WP:AGF edits while leaving a friendly message on the talkpage of the editing user.
RCMap - Geolocates anonymous edits from the IRC live feed and displays them on a world map, with links to diffs. Supports multiple languages in a unified interface.
WikiPatroller is an Android app for monitoring the recent changes feed.
Snuggle is a browser-based newcomer observation and support system, introduced in 2013. It gives a compact visual display of edits and talk page entries for accounts whose first edit was made within the past 30 days. It can be used equally to welcome well-intentioned new editors or to monitor problematic ones.
SWViewer enables you to monitor the recent changes of a wiki's in real-time. In order to use the application, local or global rollback permission is needed.
These tools extend the rollback feature by allowing you to specify a summary when using rollback. They may also offer additional features:
Navigation popups are a set of utilities that appear when hovering over wikilinks. Particularly, hovering over links of old versions provides a "revert" link.
Twinkle gives both non-administrators and administrators three types of rollback functions. Other functions include a full library of speedy deletion functions, user warnings, pseudo-automatic reporting of vandals, and more.
WMF ORES is a web service and API that provides machine learningas a service for Wikimedia projects maintained by the [[<tvar|wspt>Wikimedia Scoring Platform team</>|Scoring Platform team]]. The system is designed to help automate critical wiki-work – for example, vandalism detection and removal. Currently, the two general types of scores that ORES generates are in the context of “edit quality” and “article quality.”
Template:Vandalism information, a tool used as an indication of the current overall level of vandalism that is taking place on Wikipedia. On the page, click the edit button below the vandalism meter to change its level from 5 to 1 and/or add a short comment; 5 indicates very low levels of vandalism, and 1 indicates extremely high. You can add the vandalism information template to your userpage to stay up to date. See Template talk:Vandalism information for different styles.