Sybil attack

In open systems anyone can join without proving who they are, so a single actor can spin up thousands of nodes, accounts or addresses that look independent. The name comes from a book about a woman with multiple personalities. Proof of work and proof of stake defend blockchains against this by tying influence to computing power or staked tokens, which cannot be faked by creating more identities.

In crypto news the term most often appears around airdrops. Farmers spread activity across hundreds of wallets to claim many allocations, and projects such as Arbitrum and LayerZero ran Sybil filters, excluding wallets that behaved like clusters controlled by one entity. Governance votes and peer-to-peer networks face the same threat.

Sybil detection relies on heuristics like shared funding sources and identical transaction patterns, so it misses some farmers and flags some genuine users. Identity checks are stronger but clash with privacy and permissionless access.