Sybil Attack

An attack where a single entity creates multiple fake identities to gain disproportionate influence over a network.

What is Sybil Attack?

A Sybil attack occurs when an individual or entity manipulates a decentralized system, such as a blockchain or peer-to-peer network, by creating multiple pseudonymous identities to control a significant portion of the network’s resources or decision-making power. Named after the book Sybil about a woman with multiple personalities, this attack exploits systems that rely on the assumption that each participant is a unique entity. In the context of digital assets, Sybil attacks are particularly relevant to networks like Bitcoin or Ethereum, where attackers might create numerous fake nodes or accounts to influence consensus mechanisms, voting systems, or reputation protocols.

For example, in a proof-of-stake blockchain, an attacker could generate multiple wallet addresses to appear as distinct stakers, potentially skewing reward distribution or governance votes. To mitigate Sybil attacks, blockchains employ strategies like resource-based costs (e.g., requiring significant stake or computational power in proof-of-work systems) or identity verification mechanisms. Decentralized networks like Ethereum also use slashing penalties or economic incentives to deter malicious behavior. However, Sybil attacks remain a challenge in open, permissionless systems, as they exploit the lack of centralized identity checks, requiring robust protocol design to maintain security and fairness.