Blockchain Technology Security and Attacks 2

Question 1

What is a 'selfish mining' attack in blockchain networks?

Accepted Answer

A miner hoards discovered blocks and releases them strategically to waste honest miners' work

Answer

Selfish mining withholds blocks to make honest miners waste effort on orphaned chains, giving the attacker a disproportionate share of rewards.

Question 2

Which attack exploits the time gap between when a smart contract checks a condition and when it executes the action?

Accepted Answer

Time-of-check to time-of-use (TOCTOU) attack

Answer

A TOCTOU attack exploits the window between a condition check and execution, allowing state to change in between.

Question 3

What does a 'dust attack' target in cryptocurrency networks?

Accepted Answer

Mining pool coordination by sending tiny amounts to wallets to de-anonymize owners

Answer

Dust attacks send tiny amounts ('dust') to many addresses, then trace how those funds move to cluster addresses and break pseudonymity.

Question 4

What is the primary risk of using weak random number generation in a blockchain smart contract?

Accepted Answer

Predictable outcomes that attackers can exploit before transactions confirm

Answer

Weak randomness (e.g., using block hash or timestamp) is predictable by miners, allowing them to manipulate lottery or gambling contract outcomes.

Question 5

In blockchain security, what is an 'eclipse attack'?

Accepted Answer

Intercepting a node's network connections so it only communicates with attacker-controlled peers

Answer

An eclipse attack isolates a node by controlling all its peer connections, feeding it false information about the blockchain state.

Blockchain Practice Test