What Is Sybil Attack?
Also known as: Sybil, Sybil Attacks, Sybil Identity Attack
In short
A Sybil attack is a type of attack in which an attacker creates many fake identities, nodes or accounts to gain far more influence in a network than they actually have and to manipulate the system.
The attack takes its name from the book 'Sybil', which describes a woman with dissociative identity disorder. In peer-to-peer networks, an attacker can surround all of a target node's connections with the many nodes they control and feed it only information of their choosing; this is called an 'eclipse' attack. This way, the victim can be shown a fake view of the chain or the victim's transactions can be isolated from the network.
In blockchain applications, Sybil attacks are seen more often as exploitation of economic incentives. Examples include 'airdrop hunters' who create hundreds of wallets to claim a share of an airdrop or reward program, voting with fake accounts in governance processes that grant one vote per person, and creating artificial community engagement. Projects therefore analyze fund flows and behavioral similarities between wallets before distribution to filter out suspicious clusters.
On networks such as Bitcoin and Ethereum, a Sybil attack at the consensus level does not work on its own, because influence depends not on the number of identities but on computing power or stake; taking over these networks requires large resources, as in a 51 percent attack. Even so, diversifying node connections at the network layer and Sybil resistance measures at the application layer remain important.
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