Attack Surfaces in Blockchain Ecosystems BDC Practice Questions (Page 10)

Questions 46–47

1. 46foundation · easy

   What is a 51% attack in a proof-of-work blockchain?

   • AAn attacker exploits a bug in 51% of the smart contracts on the network
   • BAn attacker convinces 51% of users to reveal their private keys
   • CAn attacker steals 51% of the cryptocurrency in circulation
   • DAn attacker gains control of more than half of the network's mining hash rate
   Reveal Solution Discussion Select an answer first
2. 47application · medium

   A DeFi lending protocol allows users to deposit collateral and borrow stablecoins. The protocol uses a price oracle that updates every 5 minutes. An attacker takes out a flash loan, buys a large amount of a low-liquidity token, and uses that token as collateral to borrow stablecoins. The attacker then sells the token, causing its price to drop, and defaults on the loan. What is the primary risk exploited?

   • AReentrancy attack on the lending contract
   • BSybil attack on the oracle network
   • CInteger overflow in the collateral calculation
   • DOracle manipulation and liquidity pool exploitation
   Reveal Solution Discussion Select an answer first