BGP Hijacking

The core mechanism of a BGP hijack is the announcement of more specific IP prefixes or unauthorized routes into the global BGP routing table. Attackers exploit BGP's trust-based nature, where routers accept announcements from peers without cryptographic validation. This causes traffic destined for the victim's IP blocks to be rerouted through the attacker's network.

• Announcing a more specific prefix (e.g., announcing /24 when the legitimate route is /23) is often more effective, as BGP prefers the longest matching prefix.
• The announcement can be for the victim's exact prefixes (prefix hijack) or for adjacent, unused space (sub-prefix hijack).

Once the fraudulent route is propagated, the hijacker's AS becomes a transit point for the victim's traffic. This enables passive monitoring (sniffing unencrypted data) or active manipulation (modifying packets). The attacker can:

• Perform man-in-the-middle (MitM) attacks on financial transactions or login credentials.
• Cryptojack cryptocurrency miners or wallets by redirecting blockchain node communication.
• Deny service by blackholing or degrading the traffic before forwarding it on (if at all), causing outages.

This phase turns a routing anomaly into a direct security and integrity breach.

BGP hijacks are not random; they are executed with specific, often state-level or criminal, objectives.

• Espionage & Intelligence Gathering: Nation-states hijack traffic to monitor communications from specific regions or organizations.
• Cryptocurrency Theft: Redirecting traffic to and from cryptocurrency exchanges, wallets, or mining pools to steal funds or manipulate transactions.
• Censorship: A state actor can hijack routes to block access to specific services or websites.
• Monetary Gain: Some hijacks reroute traffic to generate illicit revenue from transit fees or by serving malicious ads.

Hijacks are often short-lived (minutes to hours), making detection and attribution difficult. Attackers rely on the slow convergence of BGP updates across the global internet. Key challenges include:

• Lack of Global Visibility: No single entity monitors the entire BGP routing table in real-time.
• Attribution Difficulty: While the originating AS is visible, identifying the malicious actor behind it is complex, as ASes can be compromised or leased.
• Clean-up Latency: Even after detection, withdrawing the malicious routes and restoring legitimate paths takes time, prolonging the attack's effective window.

A landmark case demonstrating global impact. Pakistan's state telecom (PTCL) attempted to block YouTube domestically by announcing YouTube's IP prefix (208.65.153.0/24) within Pakistan. This route leaked globally via PTCL's upstream provider, PCCW, and was accepted by major networks because it was a more specific /24 route. For nearly two hours, a large portion of global YouTube traffic was redirected to Pakistan, causing a worldwide outage.

This incident highlighted the fragility of BGP trust and the cascading effects of a local misconfiguration or malicious action, underscoring the need for origin validation.

These incidents are possible because the Border Gateway Protocol (BGP) operates on a trust-based model where networks automatically accept route advertisements from peers. There is no built-in mechanism to cryptographically verify that an AS is authorized to announce an IP prefix. This fundamental flaw makes blockchain networks, which rely on the underlying internet, susceptible to route poisoning and traffic interception.

To defend against BGP hijacks, blockchain projects and infrastructure providers can implement:

• Resource Public Key Infrastructure (RPKI): A framework to cryptographically sign route origins.
• BGP Monitoring & Alerting: Using services like BGPStream to detect suspicious route announcements in real-time.
• Node Diversity: Ensuring validator and node clients are distributed across multiple autonomous systems and geographic regions to reduce single points of failure.

Avoid single points of failure by connecting your node's infrastructure through multiple, geographically diverse Internet Service Providers (ISPs) or network providers. This practice, known as multi-homing, ensures that if one provider's BGP routes are hijacked, your node can maintain connectivity and consensus through an alternative path.

• Key Benefit: Significantly increases the cost and complexity for an attacker, as they must hijack all available paths simultaneously to isolate your node.

Encapsulating your node's traffic through a VPN or secure tunnel (like WireGuard or IPsec) to a trusted endpoint can bypass local routing attacks. The tunnel endpoint itself should be provisioned with strong BGP defenses (ROV, multi-homing).

• Implementation: Run your node behind a VPN; the public-facing IP is the VPN server's address, which is harder to target specifically.
• Consideration: This adds latency and relies on the security of the VPN provider's network.

If your node discovers peers via DNS-based discovery (like Ethereum's enrtree), ensure the domain records are protected with DNSSEC. This prevents DNS cache poisoning attacks, which could be used in conjunction with BGP hijacks to feed your node malicious peer lists.

• Verification: Check that your domain registrar and DNS provider support and have enabled DNSSEC for your node's discovery domain.

Configure your node's consensus client to be resilient to network-level attacks. Key settings include:

• Strict Peer Count Limits: Maintain a high number of outbound peer connections to diverse peers.
• Ignore Inbound Peers: For critical validators, consider running in outbound-only mode, connecting only to a manually configured, trusted peer list.
• Use of Checkpoint Sync: Utilize a trusted checkpoint to recover quickly if a hijack causes a chain split, ensuring you re-sync from a known valid state.

A Man-in-the-Middle (MitM) attack is a broader category of security breach where an attacker secretly intercepts and potentially alters the communication between two parties. BGP hijacking is a specific, network-layer method to execute a MitM attack. By rerouting traffic through a malicious network, the attacker can eavesdrop on data, inject malicious packets, or impersonate endpoints, which is particularly dangerous for unencrypted blockchain peer-to-peer traffic or API calls.

An Autonomous System Number (ASN) is a unique identifier assigned to a network or group of networks under a single, clearly defined routing policy, known as an Autonomous System (AS). In BGP, routes are advertised with an AS_PATH attribute listing the ASNs the announcement has traversed. Attackers manipulate this path during a hijack, often by prepending their own ASN or forging paths to make their route appear more desirable (shorter).

IP Prefix Hijacking is the specific act of illegitimately announcing ownership of IP address blocks that belong to another entity. This is the core technical action in a BGP hijack. The attacker's AS broadcasts a BGP update claiming to be the origin AS for a victim's IP range. If the malicious route is more specific (a longer prefix) or has a shorter AS path, global routers may adopt it, diverting all traffic for those IPs to the attacker's network.

Blockchain Node Diversity refers to the strategic distribution of node operators across different geographic regions, internet service providers (ISPs), and Autonomous Systems (AS). This is a critical mitigation strategy against BGP-level attacks. Concentrated node infrastructure is vulnerable to a single point of failure via a regional BGP hijack. Diverse deployment ensures network resilience, as an attacker would need to execute simultaneous, global hijacks to compromise consensus.