What is an Eclipse Attack?

Introduction

An Eclipse attack is engineered to manipulate a node’s access to information within a peer-to-peer network. By tactically disconnecting the targeted node from the broader network of participating nodes, attackers push it to rely solely on the information disseminated by the assailant. These attacks are primarily directed towards nodes that accept incoming connections, exploiting vulnerabilities through the use of botnets or phantom networks generated from host nodes.

However, by understanding the mechanics of eclipse attacks and implementing appropriate mitigation strategies, network operators and developers can safeguard their networks and enhance their resilience against such attacks. Read on to learn more.

What is an Eclipse Attack?

Eclipse attacks pose a significant threat to blockchain networks by severing a specific node’s connection to the entire network, effectively cutting off its access to both incoming and outgoing connections. This isolation can have several detrimental consequences, including delayed transaction confirmation, misinformation about the blockchain’s state, and vulnerability to double-spending attacks.

The primary aim of an eclipse attack is to hijack a node’s access to information within a peer-to-peer (P2P) network. Through manipulation of this network, attackers manage to disconnect the targeted node, effectively isolating it from the wider network of nodes participating in the blockchain. Consequently, the targeted node becomes reliant on information provided solely by the attacker regarding the blockchain’s status.

Eclipse attacks primarily target nodes that accept incoming connections, as not all nodes allow connections from other nodes. The attacker employs a botnet or phantom network, created from host nodes, to compromise the target node.

Additionally, the consequences of eclipse attacks on blockchain security and efficiency are severe. These attacks can disrupt transaction processing, lead to incorrect decision-making by nodes, split mining power, and facilitate double-spending attempts. Also, they can be used to manipulate smart contracts and reduce the overall resilience of the blockchain, potentially leading to a 51% attack.

Consequently, to mitigate the risk of eclipse attacks, blockchain networks can implement various strategies, such as diversifying peer connections, employing node discovery mechanisms, monitoring network activity, and validating blockchain data independently. These measures can help prevent nodes from being isolated and misled, thereby safeguarding the network’s integrity and operational efficiency.

How Does an Eclipse Attack Work?

Source: Marlin Protocol — The target node has been eclipsed by the attacker losing its connection with honest nodes in the network

The first step in an eclipse attack is for the attacker to fill the targeted node’s peer tables with their own malicious IP addresses. Peer tables are essentially databases that store information about other nodes in the network that a particular node is connected to. By filling these tables with their own IP addresses, the attacker ensures that the targeted node will only connect to their nodes when establishing new connections.

Once the peer tables have been manipulated, the attacker then forces the targeted node to restart either using a DDoS attack on the target, or the attacker can simply wait for it to occur. This is done in order to disrupt its current outgoing connections and reset its connection process. As the node restarts, it loses its existing connections to legitimate nodes in the network.

When the targeted node attempts to make new connections after the restart, it consults its peer tables to find potential connection partners. However, because the attacker has filled the tables with their own IP addresses, the node unknowingly establishes connections only with the attacker’s nodes. This effectively isolates the targeted node from legitimate network participants and redirects its inbound and outbound connections to the attackers’ nodes.

Source: hub.packtpub.com — The attacker’s position in the blockchain network as it isolates the targeted node from the legitimate nodes

By controlling the connections of the targeted node, the attacker can manipulate the information and traffic flowing through it. They can potentially engineer fraudulent transactions or double spending, disrupt the consensus mechanism, and even carry out more complex attacks such as a Sybil attack. The phantom network created by the attacker’s nodes serves as a gateway for executing these malicious actions and undermining the integrity and security of the blockchain network.

Eclipse Attacks on Bitcoin’s Peer-to-Peer Network

In the Bitcoin network, nodes communicate via a P2P network, forming connections to propagate transactions and blocks. Each node can have a maximum of 117 incoming TCP connections and 8 outgoing TCP connections, allowing them to interact within the network. However, an Eclipse attack can occur when an attacker gains control over a node’s connections, either by flooding it with malicious IP addresses or manipulating its connections. This control over a node’s connections can allow the attacker to control the flow of information, essentially isolating the targeted node from genuine network interactions.

Source: KAIST — Inbound and outbound TCP connections in the Bitcoin blockchain

The significance of an Eclipse attack on the Bitcoin blockchain lies in its potential to disrupt the network’s integrity. It challenges the assumption of security within Bitcoin, which relies on the presumption that as long as 51% of the mining power is honest, the system remains secure. However, this assumption assumes that all parties see all valid blocks and transactions, which an Eclipse attack can disrupt by controlling the P2P network and subsequently the blockchain information flow.

Countermeasures against Eclipse attacks in the Bitcoin network include implementing various strategies:

1. Request Time-out: Bitcoin nodes can employ time-out mechanisms, where if a node does not receive required information within a set time frame (e.g., 2 minutes for transactions or 20 minutes for blocks), it disconnects from the current peer and requests the information from another peer. This helps prevent reliance on potentially compromised nodes and improves the overall security of transactions by estimating secure waiting times.

2. Hardening Measures: Strengthening the network against Eclipse attacks involves implementing measures like group hashing, which makes attacks more challenging to execute. Group hashing requires attackers to have access to multiple IPs across different groups, increasing the complexity and resources needed to execute the attack successfully.

In essence, Eclipse attacks on Bitcoin’s P2P network pose a critical threat by potentially allowing attackers to manipulate node connections, control information flow, and undermine the security of the blockchain. However, the suggested countermeasures aim to mitigate these risks and bolster the network’s resilience against such attacks.

Consequences of an Eclipse Attack

An Eclipse attack on a blockchain network can lead to various severe consequences, significantly compromising the network’s functionality.

Here are some possible impacts of an eclipse attack:

1. Double Spending: One of the most concerning outcomes of an Eclipse attack is the potential for double-spending. This occurs when an attacker manages to make multiple transactions with the same cryptocurrency, essentially spending the same funds twice. Due to the isolation of target nodes from the wider network, they might not detect these double-spend transactions, allowing malicious actors to confirm illegitimate transactions without detection until the compromised nodes regain access to the accurate blockchain data.

Source: hub.packtpub.com — The attacker eclipses the victim node to facilitate double-spending

Further, Eclipse attacks can be categorized into 0-confirmation and N-confirmation double spend. Let’s take a closer look!

0-confirmation Double Spend: In an Eclipse attack, “0-confirmation double-spend” refers to a scenario where an attacker exploits the isolation of a node in a P2P network to fraudulently spend the same funds twice. This type of attack typically targets merchants who accept transactions without waiting for them to be confirmed on the blockchain.

N-confirmation Double Spend: In an Eclipse attack, “N-confirmation Double Spend” refers to a scenario where the attacker isolates specific nodes, such as those of merchants and miners, from the broader blockchain network. This isolation prevents these nodes from receiving timely and accurate information about the blockchain, including confirmations for transactions, leading to a potential risk of double spending, thus causing financial losses and compromising transaction integrity within the affected nodes.

1. Denial of Service (DoS): Eclipse attacks can result in a denial of service, disrupting the targeted node’s access to the network. By cutting off inbound and outbound connections, attackers can effectively render the node unable to perform its intended functions, causing disruption and potential data loss.

2. Monopolizing Connections: Attackers can monopolize the connections of a node, controlling the information flow it receives from the network. This manipulation can lead to a scenario where the targeted node solely relies on the attacker for blockchain information, facilitating fraudulent activities.

3. Spamming Addresses (IP Address): Eclipse attacks can involve spamming IP addresses, overwhelming the targeted node with an excessive volume of irrelevant data. This flooding of data can hinder the node’s performance and disrupt its operations.

4. Forcing Node Restart: In some cases, Eclipse attacks can force targeted nodes to restart repeatedly, causing downtime and hindering their ability to synchronize with the blockchain network.

5. Requiring Many Bots: Executing an Eclipse attack often necessitates a considerable number of bots or compromised nodes. This requirement makes the attack more resource-intensive but also potentially more impactful once executed.

6. Aggravated Selfish Mining and 51% Attack: Eclipse attacks can exacerbate selfish mining behaviors within the blockchain. This can lead to a scenario where malicious miners with a substantial amount of the total mining power (e.g., 40% and above) can potentially execute a 51% attack, gaining control over the blockchain and potentially reorganizing or manipulating transactions.

In essence, an Eclipse attack poses multifaceted risks to the security, reliability, and trustworthiness of a blockchain network, allowing attackers to exploit vulnerabilities for their malicious gains, particularly in terms of fraudulent transactions like double spending and drastically splitting the network mining power.

Countermeasures to Eclipse Attacks

Mitigating eclipse attacks can be challenging, as simply blocking incoming connections or restricting connections to trusted nodes may not be feasible at scale. This approach could have been a better approach to prevent eclipse attacks but it will hinder new nodes from joining the network, and limit its growth and decentralization.

To address eclipse attacks, several strategies can be employed:

1. Randomized Peer Selection: Rather than relying solely on a predetermined list of trusted nodes, a node can select its peers randomly from the pool of available nodes. This reduces the likelihood of an attacker successfully filling a node’s peer tables with their malicious IP addresses.

2. Verifiable Initialization: Nodes can use cryptographic algorithms to ensure that the initialization process is secure and verifiable. This helps prevent attackers from injecting malicious IP addresses into a node’s peer tables during the initialization phase.

3. Diverse Network Infrastructure: By using multiple independent sources for obtaining IP addresses, the network can avoid relying on a single vulnerable source. This makes it harder for an attacker to manipulate the node’s peer tables with their own IP addresses.

4. Regular Peer Table Updates: Nodes can periodically update their peer tables by obtaining the latest information from various sources. This reduces the impact of a potential eclipse attack by constantly refreshing the connections and minimizing the chances of being isolated from legitimate network participants.

5. Whitelisting: Implementing a whitelist of trusted IP addresses allows nodes to restrict connections to only legitimate peers, reducing the risk of being eclipsed by attacker-controlled nodes.

6. Network Monitoring and Analysis: Continuous monitoring of network behavior and analysis of traffic patterns can help identify any suspicious activity or potential eclipse attacks. This enables proactive detection and mitigation of such attacks before they cause significant damage.

7. Network Hardening: Strengthening the network’s overall resilience through measures such as increasing node bandwidth, optimizing routing algorithms, and enhancing consensus mechanisms can make it more resistant to eclipse attacks.

Implementing a combination of these strategies can enhance the resilience of blockchain networks against eclipse attacks and help maintain the integrity and security of the network.

Conclusion

The effects of Eclipse attacks on blockchain networks are dire, impacting security and operational efficiency. They not only disrupt transaction processes and sway node decision-making but also pose a risk of splitting mining power and enabling double-spending attempts. Additionally, Eclipse attacks could even tamper with smart contracts, weakening the overall resilience of the blockchain network and potentially leading to a 51% attack. However, by implementing the various countermeasures discussed in this article as well as specific blockchain updates, the adverse effects of this attack can be mitigated.