Network and Node Security Flashcards
6 cards from real Blockchain Technology practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Network and Node Security flashcards as text
An attacker manages to take control of a blockchain node's peer connections, ensuring all its incoming and outgoing traffic is routed through attacker-controlled nodes. This effectively isolates the victim node from the honest network, allowing the attacker to feed it false information. What is this type of network-level attack called?
Answer: An Eclipse Attack
An Eclipse Attack is a network-level attack where an adversary isolates a specific node by monopolizing all its peer connections. [11, 14] This prevents the node from receiving information from honest peers and allows the attacker to control the victim's view of the blockchain. A 51% attack involves controlling a majority of the network's consensus power, a Sybil attack involves creating many fake identities to gain influence, and a Timejacking attack manipulates a node's system clock. [1, 7]
Which of the following best describes the primary security benefit of maintaining client diversity on a blockchain network like Ethereum?
Answer: It prevents a single bug in one client implementation from causing a network-wide failure or fork.
Client diversity refers to having multiple independent software implementations of a blockchain protocol (e.g., Geth, Nethermind, Besu for Ethereum). Its main security advantage is enhancing network resilience. [4, 5] If a bug or vulnerability exists in one client, it won't affect the entire network, as nodes running other clients can continue to operate correctly, thus preventing a systemic outage. [10]
Which of the following actions constitutes a Distributed Denial-of-Service (DDoS) attack specifically targeted at the *application layer* of a blockchain network?
Answer: Repeatedly sending computationally inexpensive but valid transactions that consume significant node resources for validation.
An application-layer DDoS attack on a blockchain involves using the network's own functionalities to exhaust resources. [6] Sending a flood of valid transactions (transaction flooding) forces nodes to expend significant CPU, memory, and disk I/O to validate them, potentially slowing down or halting the processing of legitimate transactions. [16, 20] TCP SYN floods are network-layer attacks, BGP hijacking is a routing attack, and a 51% attack is a consensus-layer attack.
A node operator for a Proof-of-Stake network exposes the node's JSON-RPC endpoint to the public internet without proper authentication. The operator later discovers that the validator keys stored on the node have been used to sign a malicious message, leading to a slashing penalty. What is the MOST likely cause of this security breach?
Answer: The RPC endpoint exposed sensitive methods, allowing the attacker to remotely use the node's private keys.
Exposing RPC endpoints without proper authentication or firewall rules is a critical vulnerability. [23] Many RPC APIs include methods that can manage accounts or sign data (e.g., `personal_sign`). If these sensitive methods are exposed, an attacker can send a remote request to the endpoint and trick the node into signing messages or transactions using its private keys, leading to theft or slashing. [24, 28]
What is the primary goal of a Timejacking attack against a blockchain node?
Answer: To manipulate the node's perception of network time, potentially causing it to accept invalid blocks or reject valid ones.
A Timejacking attack specifically targets a node's system clock. By manipulating the node's time, an attacker can disrupt its ability to participate in consensus correctly. [2, 3] Because block validity often depends on timestamps falling within an acceptable range relative to the node's local time, altering this perception can cause the node to reject valid blocks from the main network or accept blocks from a malicious forked chain. [8, 13]
During the peer discovery process, a new blockchain node must find and connect to honest peers to synchronize with the network. Which of the following represents a significant security risk during this initial phase?
Answer: The node connecting exclusively to hardcoded, but malicious, bootstrap nodes.
Bootstrap nodes are the initial points of contact for a new node joining the network. If an attacker can compromise this list or trick a node into using a malicious list of bootstrap nodes, they can ensure that the new node only connects to attacker-controlled peers. This is a common method for initiating an Eclipse attack, effectively isolating the node from the start. [7, 18]