A Sybil attack is a type of cyberattack in which one participant creates and controls many fake identities or accounts within a decentralised network. The goal is to make these identities appear as independent participants and use them to gain disproportionate influence over the network. The term is commonly associated with blockchain and peer-to-peer systems, where trust and decision-making are distributed among many participants.

In a cryptocurrency network, an attacker could create a large number of nodes or identities and attempt to influence communication, voting, transaction propagation, or other network activities. Simply creating multiple identities does not necessarily give an attacker control of a blockchain because well-designed consensus mechanisms use additional requirements to make influence costly or difficult to obtain.

For example, Proof of Work requires participants to contribute computational power, while Proof of Stake generally requires participants to commit cryptocurrency as stake. These mechanisms make it harder for an attacker to gain significant influence simply by generating thousands of fake identities. Other systems may use identity verification, reputation systems, resource requirements, or specialised consensus rules to reduce Sybil risks.

A successful Sybil attack can create several problems. An attacker may attempt to isolate users from honest nodes, manipulate information, disrupt peer-to-peer communication, or influence decentralised applications. However, a Sybil attack is different from a 51% attack: controlling many identities does not automatically mean controlling the blockchain's consensus.

Sybil resistance is therefore an important part of decentralised network security. By requiring participants to demonstrate scarce resources, stake, identity, or reputation, blockchain protocols can limit the influence that fake identities have and help preserve the network's security and decentralisation.

A Sybil attack is a type of cyberattack in which one malicious participant creates multiple identities to appear as many independent users or nodes. The purpose is to gain additional influence, exploit platform incentives, or disrupt normal network activity. This threat is relevant to decentralised finance, cryptocurrency networks, online governance systems, and peer-to-peer applications. An attacker might create numerous accounts to manipulate a community vote, abuse referral bonuses, or introduce malicious nodes into a network. The potential damage depends on how the platform determines trust and distributes authority. For example, a blockchain that uses proof-of-stake considers the economic stake involved in validating transactions, rather than granting control simply because someone owns multiple wallets. Proof-of-work similarly requires computational effort. Other defences include identity checks, reputation systems, and fraud detection. While no single protection is suitable for every platform, combining appropriate security measures can reduce the effectiveness of Sybil attacks and help preserve fair participation.

A Sybil attack is a type of cyberattack in which a single person or entity creates multiple fake identities to gain unfair influence over a network or online system. This attack is particularly relevant to blockchain networks, peer-to-peer systems, and decentralised applications. By controlling numerous identities, an attacker may manipulate voting processes, disrupt network operations, spread false information, or exploit reward programs.

In cryptocurrency networks, Sybil attackers may create multiple wallets or accounts to influence governance decisions, manipulate airdrop distributions, or collect rewards intended for genuine users. For example, someone might create hundreds of wallets to claim tokens from a project that limits rewards to one participant. These actions can undermine fairness and reduce trust in decentralised platforms.

To prevent Sybil attacks, projects use various security measures, including identity verification, economic requirements, reputation systems, and advanced detection algorithms. Proof-of-work and proof-of-stake mechanisms can also make certain attacks more expensive. Although eliminating Sybil attacks is difficult, effective security measures can significantly reduce their impact on decentralised networks.