Definition
A Sybil attack is a class of security attack in which a single entity forges or acquires control over multiple distinct identities within a distributed system. In blockchain and crypto networks, these identities can correspond to accounts, nodes, or validators that appear independent but are secretly coordinated. The attacker’s goal is to distort consensus, voting, or reputation mechanisms by amplifying their effective presence in the system. Sybil resistance is therefore a core design concern for public, permissionless networks and decentralized governance structures.
In the context of decentralized autonomous organizations (DAOs) and on-chain or off-chain voting, a Sybil attack can allow one actor to dominate outcomes by masquerading as many participants. When governance power is tied to addresses or accounts rather than robust identity or stake-based constraints, the system becomes more vulnerable to this type of manipulation. Many consensus protocols and governance frameworks explicitly incorporate Sybil-resistance assumptions, such as economic costs or identity verification, to limit the feasibility of such attacks.
Context and Usage
Sybil attacks are discussed whenever a protocol’s security depends on counting participants, votes, or nodes as if they were independent actors. In proof-of-stake or similar systems, validators are often weighted by stake rather than raw identity count to reduce the impact of cheaply created identities. In DAO governance, the distribution and concentration of governance tokens, as well as voting mechanisms used in tools like Snapshot, are analyzed for their susceptibility to Sybil-style manipulation.
The term is used both for concrete exploits and as a theoretical threat model when designing network, consensus, or voting rules. Security analyses often distinguish between systems that are inherently Sybil-resistant, where creating many identities does not meaningfully increase control, and those that are Sybil-vulnerable, where identity creation is low-cost and directly translates into influence. In blockchain ecosystems, understanding Sybil attacks is essential for evaluating the robustness of validator sets, node-based reputation schemes, and token-weighted governance processes.