Attack Surfaces in Blockchain Ecosystems BDC Practice Questions (Page 8)

Questions 36–40

1. 36expert · hard

   A DeFi protocol uses a price oracle that reads from a single centralized exchange. The protocol allows users to open leveraged positions. An attacker notices that the exchange's API can be slow to update during high volatility. What is the most effective way to mitigate the risk of oracle manipulation?

   • ARequire users to provide additional collateral to open positions.
   • BAdd a circuit breaker that pauses trading if the price deviates by more than 5% from the previous block.
   • CUse a decentralized oracle network that aggregates prices from multiple independent sources and provides a time-weighted average price (TWAP).
   • DIncrease the leverage limit to allow users to profit more from price movements.
   Reveal Solution Discussion Select an answer first
2. 37expert · hard

   A decentralized autonomous organization (DAO) uses a governance token to vote on protocol upgrades. An attacker acquires a large number of tokens through a flash loan, then submits a proposal to transfer treasury funds to their own address. The proposal passes because the attacker's temporary voting power exceeds the quorum. Which vulnerability is being exploited, and what is the MOST effective mitigation?

   • AOracle manipulation; use a decentralized oracle for token prices.
   • BReentrancy attack; add a reentrancy guard to the proposal function.
   • CPhishing attack; require multi-signature for all governance actions.
   • DGovernance attack via flash-loan voting; use time-weighted voting power or a voting delay.
   Reveal Solution Discussion Select an answer first
4. 38foundation · easy

   What is a flash loan attack in DeFi?

   • AAn attacker sends a phishing email to trick users into revealing their private keys
   • BAn attacker creates multiple fake identities to gain voting power in a DAO
   • CAn attacker floods the network with transactions to slow down block production
   • DAn attacker borrows a large amount of assets without collateral and repays within the same transaction to exploit price differences or vulnerabilities
   Reveal Solution Discussion Select an answer first
5. 39foundation · easy

   Which smart contract vulnerability occurs when arithmetic operations exceed the maximum or minimum value that a variable can hold?

   • AAccess control flaw
   • BInteger overflow/underflow
   • CReentrancy
   • DDenial of service
   Reveal Solution Discussion Select an answer first
6. 40application · medium

   A proof-of-work blockchain has a small number of miners. An attacker controls a large portion of the network's hash rate and decides to rewrite the blockchain to double-spend coins. Which attack is this, and what is a common defense?

   • ALong-range attack; use checkpointing.
   • BSelfish mining; use a different block reward scheme.
   • CEclipse attack; use more peers per node.
   • D51% attack; increase the network's hash rate or use a different consensus mechanism.
   Reveal Solution Discussion Select an answer first