Eclipse Attack

An eclipse attack is a network-level attack on a blockchain node where an attacker monopolizes all of the victim node's peer connections. Once "eclipsed," the node only communicates with attacker-controlled peers and receives a false view of the blockchain.

How it works

1. The attacker discovers the victim node's IP address
2. The attacker floods the victim with connection requests from many controlled nodes
3. The victim's peer slots fill up with attacker nodes; legitimate peers are crowded out
4. The attacker can now feed the victim fraudulent blocks, fake transaction confirmations, or withhold real blocks

Potential consequences

• Double-spend fraud — merchant running an eclipsed node accepts a payment that the real network never confirmed
• Mining waste — an eclipsed miner builds on a false chain, wasting hashrate on work the network will reject
• Selfish mining assistance — attacker delays block propagation to gain an unfair advantage

Who is most at risk

• Solo miners with few peer connections
• Light clients (SPV wallets) that don't download the full blockchain
• Nodes with predictable IP addresses or weak peer diversity

Defenses

• Connecting to many diverse peers across different ASNs
• Using the Tor network or VPNs to vary apparent IP
• Increasing the number of outbound connections
• Bitcoin Core and other major clients have hardened against eclipse attacks with randomized peer selection

See also

• Blockchain
• Proof of Work
• Double spending