Although it is not clear why these DeFi hackers returned some of their ill-gotten gains, one possible explanation is conscience.

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In the case of flash loans, an attacker receives a loan from a DeFi protocol, spends the loan funds, and returns the loan all in the same smart contract transaction. Since the entire process of lending occurs in the same smart contract transaction, no collateral is required.

Basically, anyone can take out a flash loan without collateral, just by paying the associated fees. Analysts at on-chain analysis firm Glassnode explained:

"This means that users of flash loans, including hackers, only need to take very small risk; if the transaction does not achieve 'break even', the borrower cannot repay the loan, then the entire transaction will be reversed, which means that users only There will be a loss of gas fees. The potential gains are objective in comparison.”

If the hacker uses the loan capital to arbitrage in the short term, he will still make money after repaying the borrowed principal.

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The sentiment surrounding the flash loan attack in the DeFi space remains mixed. On the one hand, these events can be considered as attacks or vulnerabilities because they resulted in the loss of user funds. But, on the other hand, some argue that flash loans are not illegal and follow the rules and systems of the platforms to which they belong.

Perhaps some attackers belonged to the former camp, and the reason why they returned the funds was to not harm innocent users.

For example, on November 15, Value DeFi suffered a flash loan attack, resulting in a loss of $6 million. The attacker borrowed 80,000 ETH, worth just under $40 million, from DeFi protocol Aave. Then, the attacker used the two stablecoins DAI and USDC to arbitrage, sacrificing the interests of Value DeFi users and making a fortune. The attacker then returned the $40 million principal to Aave.

Su Zhu, chief executive of Three Arrows Capital, said the hacker also returned $2 million in profits he made on flash loans. He pointed out that this kind of attack can be done even without flash loans, but only whales or high-net-worth investors have the ability to do so.

According to Su, the attacker left a message asking, "Do you really know about flash loans?" and returned the $2 million as a friendly gesture. According to Su, this act is intended to remind everyone that the same "attack" is technically possible even without flash loans — but only for super-wealthy whales.

Another hacker also returned $50,000 after learning that the victim who lost $100,000 in his attack was a nurse.

Similarly, on October 26, Harvest was hit with a $24 million flash loan attack as a hacker used its liquidity pools for arbitrage. After the incident, the hackers returned $2.5 million.

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