Sybil Attack
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In Brief
A Sybil attack floods a network with many fake identities controlled by one attacker to gain outsized influence — the reason blockchains tie voting power to something costly, like computing work or staked capital, instead of identities.
What Is a Sybil Attack?
A Sybil attack is an attempt to control or manipulate a network by creating many fake identities that all answer to one attacker. If influence in a system is counted per identity — one node, one vote — then whoever can manufacture identities cheaply can manufacture influence, outvoting honest participants without owning real resources.
The name comes from a famous case study of a patient with multiple personalities. In open networks where anyone can join anonymously, resisting Sybil attacks is a foundational design problem.
Where Sybil Attacks Show Up
Peer-to-peer networks: an attacker running many nodes can surround a victim's node and feed it a false view of the network.
Governance: votes counted per wallet invite one person to vote from thousands of wallets.
Airdrops: "Sybil farmers" create armies of wallets to claim rewards meant for genuine individual users.
Reviews and social signals: fake accounts inflate a project's apparent community and credibility.
How Blockchains Defend Themselves
Blockchains solve the core problem by making influence expensive rather than identity-based. Proof of work ties block production to real computation; proof of stake ties it to real capital that can be slashed. Creating a million node identities gains an attacker nothing if influence is measured in hash power or stake. At the application layer, projects fight Sybils with eligibility criteria, on-chain history analysis, and proof-of-personhood systems.
Sybil Attacks and Trust Wallet
Sybil resistance is why decentralized networks can be trustworthy without gatekeepers — and it protects the chains your assets live on. Trust Wallet keeps those assets in self-custody across 100+ blockchains, and requires no account or identity to use: your keys, not a profile, are what count.