Bitcoin-focused DeFi protocol Echo was hit by a hacking attack on May 18, local time.

The incident first became known after an anonymous crypto influencer, DCF GOD, shared details on social media platform X on the afternoon of May 18, The Block reported.

Onchain Lens said the attacker minted 1,000 eBTC, a bitcoin liquidity token issued by Echo on the Monad chain. The attacker deposited 45 eBTC as collateral on DeFi lending protocol Convergence and borrowed about 11.29 WBTC, worth about $867,700 at the time. The attacker bridged the WBTC to Ethereum and exchanged it for ETH. The attacker moved 385 ETH to crypto mixer Tornado Cash.

The attacker still holds 955 eBTC, worth about $73.2 million, The Block reported.

Monad and Convergence confirmed the attack. Keone Hon (키온 혼), a co-founder of Monad, said security researchers were investigating the incident and the network itself was not affected. He said security researchers had determined about $816,000 was stolen in the attack.

Convergence said other markets were not affected thanks to a fully isolated market structure and there were no signs of smart contract compromise. Convergence temporarily suspended the relevant eBTC market as a precaution.

On May 19, Echo announced the attack occurred after a service administrator key used on the Monad chain was stolen. Echo said it recovered the key and burned the 955 eBTC the attacker had held. DeFiLlama said there were 13 DeFi protocol security breaches in May alone, excluding the Echo case.