Blockchain Security Training Network and Node Security 2 — Questions and Answers
Question 1: An attacker monopolizes all of a victim node's peer connections to control its view of the network. What attack is this?
- Eclipse attack (Correct answer)
- Replay attack
- Dusting attack
- Phishing attack
Correct answer: Eclipse attack
An eclipse attack isolates a node by occupying all its inbound and outbound connections so the attacker controls everything it sees.
Question 2: Which practice best protects a validator node's signing keys?
- Store keys in a hardware security module or remote signer (Correct answer)
- Keep keys in plaintext on the validator host
- Email keys to a backup account
- Hardcode keys in the client config
Correct answer: Store keys in a hardware security module or remote signer
Isolating signing keys in an HSM or remote signer keeps them off the internet-facing node and limits exposure.
Question 3: What is the primary purpose of running a node behind a firewall that only exposes the P2P port?
- Reduce attack surface by blocking unneeded ports (Correct answer)
- Increase block reward
- Speed up transaction signing
- Bypass consensus rules
Correct answer: Reduce attack surface by blocking unneeded ports
Limiting open ports to only what the node needs shrinks the attack surface available to remote adversaries.
Question 4: A node operator notices the RPC interface is reachable from the public internet. What is the main risk?
- Unauthorized access to node management and wallet functions (Correct answer)
- Faster block propagation
- Higher staking yield
- Improved peer discovery
Correct answer: Unauthorized access to node management and wallet functions
Exposed RPC endpoints can let attackers query or control the node and potentially drain hot wallets.
Question 5: Which DNS-related weakness can mislead a new node during initial peer discovery?
- Poisoned DNS seed returning attacker-controlled peers (Correct answer)
- Slow DNS lookups only
- DNS caching of valid records
- Encrypted DNS queries
Correct answer: Poisoned DNS seed returning attacker-controlled peers
If DNS seeds are poisoned, a bootstrapping node may connect only to malicious peers, enabling eclipse-style isolation.
Question 6: Why is keeping node client software updated a security priority?
- Patches fix known consensus and network vulnerabilities (Correct answer)
- It increases the block size automatically
- It removes the need for a firewall
- It guarantees higher rewards
Correct answer: Patches fix known consensus and network vulnerabilities
Updates close disclosed vulnerabilities that attackers could otherwise exploit against the network or node.
Question 7: What does a Sybil attack rely on to influence a peer-to-peer network?
- Creating many fake identities or nodes (Correct answer)
- Encrypting all traffic
- Reducing the number of validators
- Increasing gas fees
Correct answer: Creating many fake identities or nodes
A Sybil attack floods the network with many fake nodes to gain disproportionate influence over routing or consensus.
Blockchain Security Training Network and Node Security 2
An attacker monopolizes all of a victim node's peer connections to control its view of the network.
What attack is this?