Eclipse Attack Meaning

An eclipse attack is a network-level attack in which a malicious actor isolates a specific node, or a small group of nodes, within a peer-to-peer blockchain network. Instead of attempting to disrupt the entire network, the attacker focuses on controlling all incoming and outgoing connections of the targeted node. Once isolated, the victim node can no longer see the true state of the network and is fed manipulated or incomplete information by the attacker.

This type of attack exploits the fact that nodes in decentralized networks cannot maintain connections with every other participant. For scalability and efficiency reasons, nodes typically connect to a limited number of peers. In blockchains such as Bitcoin, this cap creates an opportunity for attackers to monopolize a node’s peer list.

By flooding the network with attacker-controlled nodes or IP addresses, the attacker can gradually replace legitimate peers with malicious ones. The consequences of an eclipse attack can be serious. An isolated node may be tricked into accepting invalid blocks or transactions, delayed from seeing new blocks, or manipulated into wasting computational resources.

When miners or validators are eclipsed, the attack can escalate into more severe outcomes, such as double-spending attacks, selfish mining advantages, or even facilitating broader consensus manipulation. Wallets and exchanges relying on compromised nodes may also display incorrect balances or transaction states. Executing an eclipse attack usually involves several steps: identifying a target node, overwhelming its existing connections through denial-of-service techniques, and then filling its peer table with attacker-controlled nodes.

Once control is established, the attacker dictates what the victim sees, effectively creating a false version of reality for that node. Defenses against eclipse attacks include diversifying peer selection, randomizing connections, limiting repeated connections from the same IP ranges, and regularly rotating peers. Some blockchain clients implement protections such as outbound peer diversity and connection throttling to reduce attack feasibility.

While eclipse attacks are complex and resource-intensive, they highlight that decentralization alone does not eliminate network-layer vulnerabilities. Robust peer discovery, monitoring, and redundancy are critical for maintaining the integrity of decentralized systems.