DDoS

A Distributed Denial of Service (DDoS) attack, when performed against a blockchain, involves the attacker overwhelming the network with more requests, connections, or transactions than it can process. This leads to severe congestion, making users unable to access the network until the attack subsides.

Blockchains have some resistance to these attacks due to the ability of the network to survive individual node failures, and the existence of transaction fees on most public blockchains helps to make transaction flooding attacks expensive to initiate and maintain.