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" or "hivemind". Anonymous members (known as anons) can sometimes be distinguished in public by the wearing of Guy Fawkes masks in the style portrayed in the graphic novel and film V for Vendetta. Some anons also opt to mask their voices through voice changers or text-to-speech programs.

Dozens of people have been arrested for involvement in Anonymous cyberattacks in countries including the United States, the United Kingdom, Australia, the Netherlands, South Africa, Spain, India, and Turkey. Evaluations of the group's actions and effectiveness vary widely. Supporters have called the group "freedom fighters" and digital Robin Hoods, while critics have described them as "a cyber lynch mob" or "cyber terrorists". In 2012, Time called Anonymous one of the "100 most influential people" in the world. Anonymous' media profile diminished by 2018, but the group re-emerged in 2020 to support the George Floyd protests and other causes.

1. Philosophy

The philosophy of Anonymous offers insight into a long-standing political question that has gone unanswered with often tragic consequences for social movements: What does a new form of collective politics look like that wishes to go beyond the identity of the individual subject in late capitalism?

Internal dissent is also a regular feature of the group. A website associated with the group describes it as "an internet gathering" with "a very loose and decentralized command structure that operates on ideas rather than directives". Gabriella Coleman writes of the group. "In some ways, it may be impossible to gauge the intent and motive of thousands of participants, many of who don't even bother to leave a trace of their thoughts, motivations, and reactions. Among those that do, opinions vary considerably".

Broadly speaking, Anons oppose Internet censorship and control and the majority of their actions target governments, organizations, and corporations that they accuse of censorship. Anons were early supporters of the global Occupy movement and the Arab Spring. Since 2008, a frequent subject of disagreement within Anonymous has been whether members should focus on pranking and entertainment or more serious (and in some cases, political) activism.

We [Anonymous] just happen to be a group of people on the Internet who need - just kind of an outlet to do as we wish, that we wouldn't be able to do in regular society ... That's more or less the point of it. Do as you wish ... There's a common phrase: 'we are doing it for the lulz'.

— Trent Peacock, Search Engine: The Face of Anonymous, February 7, 2008.

Because Anonymous has no leadership, no action can be attributed to the membership as a whole. Parmy Olson and others have criticized media coverage that presents the group as well-organized or homogenous: Olsen writes, "There was no single leader pulling the levers, but a few organizational minds that sometimes pooled together to start planning a stunt". 

Some members protest using legal means, while others employ illegal measures such as DDoS attacks and hacking. Membership is open to anyone who wishes to state they are a member of the collective; British journalist Carole Cadwalladr of The Observer compared the group's decentralized structure to that of al-Qaeda.

"If you believe in Anonymous, and call yourself Anonymous, you are Anonymous".

Olson, who formerly described Anonymous as a "brand", stated in 2012 that she now characterized it as a "movement" rather than a group: "Anyone can be part of it. It is a crowd of people, a nebulous crowd of people, working together and doing things together for various purposes.

The group's few rules include not disclosing one's identity, not talking about the group, and not attacking the media. Members commonly use the tagline, "We are Anonymous. We are Legion. We do not Forgive. We do not Forget. Expect Us". Brian Kelly writes that three of the group's key characteristics are;

1. An unrelenting moral stance on issues and rights, regardless of direct provocation.
2. A physical presence that accompanies online hacking activity, and
3. A distinctive brand.

Journalists have commented that Anonymous secrecy, fabrications, and media awareness pose an unusual challenge for reporting on the group's actions and motivations. Quinn Norton of Wired writes that: "Anons lie when they have no reason to lie. They weave vast fabrications as a form of performance. Then they tell the truth at unexpected and unfortunate times, sometimes destroying themselves in the process. They are unpredictable".

Norton states that the difficulties in reporting on the group cause most writers, including herself, to focus on the "small groups of hackers who stole the limelight for a legion, defied their values, and crashed violently into the law" rather than "Anonymous's sea of voices, all experimenting with new ways of being in the world".