Practice Test Geeks(CBSE) Certified Blockchain Security Expert Practice Test
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Node and Network Security Flashcards

7 cards from real CBSE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Node and Network Security flashcards as text

  1. A blockchain validator node is targeted by an attacker who controls 51% of peers and delays block propagation to all other honest nodes. What is this strategy called?

    Answer: Network partitioning with block withholding

    By partitioning the honest network and withholding new blocks, the attacker can force honest miners onto a stale chain while the attacker's chain grows ahead.

  2. Which firewall rule set best protects a Bitcoin full node while still allowing legitimate peer-to-peer traffic on mainnet?

    Answer: Allow inbound TCP 8333, block all other inbound; allow all outbound

    Bitcoin P2P runs on TCP 8333; restricting other inbound ports limits attack surface while allowing peers to connect, and blocking RPC port 8332 from inbound prevents remote RPC abuse.

  3. What does 'transaction malleability' allow an attacker to do at the network level before a transaction is confirmed?

    Answer: Alter the transaction ID (txid) by modifying the scriptSig without changing its validity

    Transaction malleability lets a third party tweak the scriptSig data, producing a different txid for the same economic transaction, which can confuse tracking systems.

  4. A node operator wants to mitigate Sybil attacks in their private blockchain network. Which identity mechanism provides the strongest resistance?

    Answer: Permissioned membership with certificate-based node identity (e.g., X.509 via a CA)

    Certificate-based identity ties each node to a CA-issued credential, making it expensive for an attacker to create unlimited fake identities.

  5. Which metric in node monitoring most directly indicates an ongoing eclipse attack against a blockchain node?

    Answer: All peer connections resolving to the same ASN or IP subnet

    Eclipse attacks rely on filling the victim's peer table with attacker-controlled nodes, so seeing all peers from a single ASN or narrow IP range is a strong indicator.

  6. In a proof-of-stake network, what type of node-level attack attempts to manipulate a validator's local clock to make it sign blocks for a future slot?

    Answer: Timejacking

    Timejacking shifts the victim node's network-adjusted time by advertising false timestamps from multiple peers, causing it to accept or produce blocks at incorrect times.

  7. Which protocol feature in libp2p (used by Ethereum 2.0 and Filecoin) is specifically designed to resist network-level censorship of node discovery?

    Answer: Kademlia DHT with peer routing

    Kademlia DHT distributes peer discovery information across many nodes, making it resilient to censorship because no single node controls the routing table.