FREE Blockchain Security Training Blockchain Network-Level Attacks Questions and Answers

Question 1

An attacker targets a specific mining node by gaining control of its router.
They ensure all of the node's outgoing peer connections are exclusively established with malicious nodes controlled by the attacker.
The victim's node continues to operate but only sees a fraudulent version of the blockchain.
What type of network-level attack is this?

Accepted Answer

Eclipse Attack

Answer

BGP Hijacking

Answer

Sybil Attack

Answer

DDoS Attack

Question 2

Which of the following best describes how a BGP (Border Gateway Protocol) hijacking attack can be used to disrupt a blockchain network?

Accepted Answer

By maliciously re-routing internet traffic intended for major nodes or mining pools to a location controlled by the attacker.

Answer

By creating a large number of pseudonymous nodes to outvote honest participants.

Answer

By altering the transaction ID of a broadcasted transaction before it is mined.

Answer

By manipulating a node's internal clock to make it reject valid blocks from the network.

Question 3

A network attacker successfully manipulates the Network Time Protocol (NTP) responses received by a blockchain node, causing its system clock to be significantly skewed. The node begins rejecting new, valid blocks because their timestamps appear to be too far in the future according to its incorrect local time. This attack is known as:

Accepted Answer

Timejacking

Answer

A Finney Attack

Answer

Timestamp Grinding

Answer

A Long-Range Attack

Question 4

A large, public blockchain network experiences a sudden degradation in performance. Investigation reveals that a significant number of publicly accessible full nodes are being flooded with an overwhelming volume of garbage P2P messages and transaction requests, consuming their bandwidth and CPU. This prevents them from relaying valid transactions and blocks. What is the most likely network-level attack occurring?

Accepted Answer

Distributed Denial-of-Service (DDoS) Attack

Answer

Selfish Mining

Answer

Eclipse Attack

Answer

Transaction Malleability

Question 5

Which of the following accurately describes a transaction malleability attack at the network level?

Accepted Answer

An attacker modifies the digital signature of a valid, unconfirmed transaction in a way that changes the transaction ID (TXID) but not the fundamental validity of the transfer.

Answer

An attacker intercepts a transaction and resubmits it with a higher fee to get it mined first.

Answer

An attacker floods a node with invalid transactions, causing it to waste computational resources.

Answer

An attacker isolates a node from the network and feeds it a false version of the blockchain.

Question 6

A sophisticated actor physically disrupts the primary undersea fiber optic cables connecting two continents. For several hours, blockchain nodes in Region A can only communicate with other nodes in Region A, and nodes in Region B can only communicate with other nodes in Region B. What is the most direct consequence of this network partitioning attack?

Accepted Answer

The network will fork into two separate, valid chains that will need to be reconciled when connectivity is restored.

Answer

All transactions will fail globally until the connection is restored.

Answer

The total network hashrate will be permanently reduced by 50%.

Answer

A single mining pool will immediately gain control of the entire network.