Anonymous originated in 2003 on the imageboard 4chan, representing the concept of many online and offline community users simultaneously existing as an anarchic, digitized global brain.^[4][5][6] Anonymous members (known as "Anons") can be distinguished in public by the wearing of Guy Fawkes masks in the style portrayed in the graphic novel and film V for Vendetta.^[7]

In its early form, the concept was adopted by a decentralized online community acting anonymously in a coordinated manner, usually toward a loosely self-agreed goal, and primarily focused on entertainment, or "lulz". Beginning with 2008's Project Chanology—a series of protests, pranks, and hacks targeting the Church of Scientology—the Anonymous collective became increasingly associated with collaborative hacktivism on a number of issues internationally. Individuals claiming to align themselves with Anonymous undertook protests and other actions (including direct action) in retaliation against copyright-focused campaigns by motion picture and recording industry trade associations. Later targets of Anonymous hacktivism included government agencies of the U.S., Israel, Tunisia, Uganda, and others; the Islamic State of Iraq and the Levant; child pornography sites; copyright protection agencies; the Westboro Baptist Church; and corporations such as PayPal, MasterCard, Visa, and Sony. Anons have publicly supported WikiLeaks and the Occupy movement. Related groups LulzSec and Operation AntiSec carried out cyberattacks on U.S. government agencies, media, video game companies, military contractors, military personnel, and police officers, resulting in the attention of law enforcement to the groups' activities. Some actions by members of the group have been described as being anti-Zionist. It has threatened to cyber-attack Israel and engaged in the "#OpIsrael" cyber-attacks of Israeli websites on Yom HaShoah (Holocaust Remembrance Day) in 2013.^[8]

Dozens of people have been arrested for involvement in Anonymous cyberattacks, in countries including the U.S., UK, Australia, the Netherlands, Spain, India and Turkey. Evaluations of the group's actions and effectiveness vary widely. Supporters have called the group "freedom fighters"^[9] and digital Robin Hoods^[10] while critics have described them as "a cyber lynch-mob"^[11] or "cyber terrorists".^[12] In 2012, Time called Anonymous one of the "100 most influential people" in the world.^[13]

The name Anonymous itself is inspired by the perceived anonymity under which users post images and comments on the Internet. Usage of the term Anonymous in the sense of a shared identity began on imageboards, particularly the /b/ board of 4chan, dedicated to random content. A tag of Anonymous is assigned to visitors who leave comments without identifying the originator of the posted content. Users of imageboards sometimes jokingly acted as if Anonymous was a single individual. The concept of the Anonymous entity advanced in 2004 when an administrator on the 4chan image board activated a "Forced_Anon" protocol that signed all posts as Anonymous.^[29] As the popularity of imageboards increased, the idea of Anonymous as a collective of unnamed individuals became an Internet meme.^[30]

Users of 4chan's /b/ board would occasionally join into mass pranks or raids. In a raid on July 12, 2006, for example, large numbers of 4chan readers invaded the Finnish social networking site Habbo Hotel with identical avatars; the avatars blocked regular Habbo members from accessing the digital hotel's pool, stating it was "closed due to fail and AIDS".^[31] Future LulzSec member Topiary became involved with the site at this time, inviting large audiences to listen to his prank phone calls via Skype.^[32][a] Due to the growing traffic on 4chan's boards, users soon began to plot pranks offline using Internet Relay Chat (IRC).^[34] These raids resulted in the first mainstream press story on Anonymous, a report by Fox station KTTV in Los Angeles, California in the U.S. The report called the group "hackers on steroids", "domestic terrorists", and an "Internet hate machine".^[28][35]

Encyclopedia Dramatica was founded in 2004 by Sherrod DiGrippo, initially as a means of documenting gossip related to livejournal, but it quickly was adopted as a major platform by Anonymous for satirical and other purposes.^[36] The not safe for work site celebrates a subversive "trolling culture", and documents Internet memes, culture, and events, such as mass pranks, trolling events, "raids", large-scale failures of Internet security, and criticism of Internet communities that are accused of self-censorship in order to gain prestige or positive coverage from traditional and established media outlets. Journalist Julian Dibbell described Encyclopædia Dramatica as the site "where the vast parallel universe of Anonymous in-jokes, catchphrases, and obsessions is lovingly annotated, and you will discover an elaborate trolling culture: Flamingly racist and misogynist content lurks throughout, all of it calculated to offend."^[36] The site also played a role in the anti-Scientology campaign of Project Chanology.^[37]

On April 14, 2011, the original URL of the site was redirected to a new website named Oh Internet that bore little resemblance to Encyclopedia Dramatica. Parts of the ED community harshly criticized the changes.^[38] In response, Anonymous launched "Operation Save ED" to rescue and restore the site's content.^[39] The Web Ecology Project made a downloadable archive of former Encyclopedia Dramatica content.^[40][41] The site's reincarnation was initially hosted at encyclopediadramatica.ch on servers owned by Ryan Cleary, who later was arrested ^[42] in relation to attacks by LulzSec against Sony.^{[citation needed]}