April 18, 2021

Hacker Prevents $ 10 Million Theft From Vulnerable DeFi Protocol Expert …

Hacker Prevents Theft Of $ 10 Million From Vulnerable DeFi Protocol

Blockchain security expert and ethical hacker samczsun has published a detailed analysis of the operation to rescue 25,000 ETH or about $ 10 million from a vulnerable smart contract on the Ethereum network.

While researching smart contracts in search of vulnerabilities on September 15, samczsun stumbled upon the Lien Finance protocol. It turned out that anyone could withdraw cryptocurrency from it.

Hacker Prevents $ 10M Theft From Vulnerable DeFi Protocol Blockchain Security Expert and Ethical ...

The Lien contract contained a “burn” feature that allowed users to issue worthless tokens and exchange them for Ether. Luckily for developers and users, the author of the blog post was the first to stumble upon the vulnerability.

We considered two options for getting out of this situation. The Lien team could have publicly disclosed the vulnerability, but in that case, attackers would certainly have exploited it. Direct withdrawal of assets from the contract by exploiting a bug was also not safe due to the presence of bots that could carry out the same operation with a higher commission or with the assistance of miners and appropriate the cryptocurrency.

The audit company CertiK and the SparkPool mining pool were connected to the procedure. With their help, a special API was developed that allowed miners to independently send and receive transactions without disclosing them in the mempool.

Also, four signed transactions were prepared. The withdrawal of funds was again carried out indirectly. This required the transfer of 30,000 SBT and LBT tokens, available for issue in unlimited volumes, and converting them to ETH through the burn function.

Hacker Prevents $ 10M Theft From Vulnerable DeFi Protocol Blockchain Security Expert and Ethical ...

“I hesitated for a while, but we did our best,” the author writes. – We could have lost $ 9.6 million, but we would not regret anything. The 15 blocks that passed before our transactions were added felt like hours, but finally the transactions were added flawlessly, in order, and not reversed. “.

Then the Lien Finance team had only to exchange SBT and LBT tokens for ETH using the burn function. After a short time, confirmation of the successful rescue of 25,000 ETH appeared on the blockchain.

Hacker Prevents $ 10M Theft From Vulnerable DeFi Protocol Blockchain Security Expert and Ethical ...

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