What Is a Denial-of-Service (DoS) Attack Related to Fallback Functions?

A DoS attack related to fallback functions occurs when a malicious contract's fallback function is intentionally designed to consume excessive gas or always revert. If a vulnerable contract tries to send Ether to this malicious contract using transfer or send , the transaction will fail.

If the vulnerable contract relies on sending Ether to a list of users, the malicious contract can block the entire function for all other users.