TLDR
- Flash loan attacks caused $1.211 billion in losses across 72 incidents between February 2020 and July 2024.
- Those attacks made up 18.44% of the $6.568 billion lost in 254 total DeFi exploits during the same period.
- More than 80% of flash loan losses happened on Ethereum.
- Four attack types, including one $181 million governance exploit, caused over 81% of total losses.
- Logic exploits grew from 28% to 55% of flash loan losses as attackers shifted tactics over time.
Flash loan attacks drained $1.211 billion from decentralized finance platforms between February 2020 and July 2024. The figure comes from a new study published in the Journal of Financial Crime.
The research was done by Professor Tim Hall of the University of Winchester and Remo Stieger, a former partner at Swiss risk intelligence firm SyntiFi. It found 72 flash loan attacks among 254 total DeFi exploits in that window.
A flash loan lets someone borrow funds without putting up collateral. The loan must be repaid within the same blockchain transaction, or the whole transaction is reversed. This makes them useful for trading, but attackers can also use them to borrow large sums for a few seconds at almost no cost.
How the Study Was Done
The team scanned 20.63 billion blockchain transactions across seven networks. These included Ethereum, Base, Optimism, Arbitrum, BNB Chain, Avalanche, and Polygon.
The university says this is the first study to combine criminal research methods with on-chain data in this way. The full paper was behind a paywall, so some details here come from the university’s summary rather than the complete text.
Where the Losses Came From
More than 80% of flash loan losses happened on Ethereum. The researchers sorted attacks into 14 types, split into two groups: price feed manipulation and protocol logic flaws.
Four attack types caused over 81% of all losses. These were price oracle attacks, donate function exploits, reentrancy attacks, and one governance attack that alone cost $181 million.
Logic exploits were rarer but cost more per attack. They made up 28% of flash loan losses from 2020 to early 2022, then rose to 55% from 2022 to mid-2024.
Individual attacks ranged from $80,000 to $197 million. Attacks of $10 million or more made up over 88% of total losses.
The study includes an account from one platform hit by a flash loan attack. Its bug had passed internal checks and several outside auditors, then sat on-chain unnoticed for over a year.
The attacker later taunted the platform online, according to Hall. This led some victims to contact the attacker directly about the damage the loss caused them.
The platform’s representative split attackers into two groups: hobbyist researchers and professional state-linked or organized crime groups, naming North Korea as one example. The representative said professional attacks are “not at all advanced” from a technical standpoint.
The same representative said attacks often break apart the teams behind affected platforms, even when stolen funds are later returned.
Losses topped 0.5% of total flash loan borrowing volume in only one six-month stretch of the study period. Flash loan usage kept rising the entire time.
The authors describe the attacks as increasingly complex and harder to predict, but not a threat to DeFi’s survival. They stress that flash loans themselves are legal tools, and the attacks exploit weaknesses in the platforms around them.
The study period ended in July 2024, but related damage has continued since. Bunni, a decentralized exchange, shut down in October 2025 after an $8.4 million exploit tied to flash loan manipulation and a rounding error in its pricing system.
The post Flash Loan Attacks Cost DeFi $1.2 Billion Over Four Years, Study Finds appeared first on Blockonomi.
This articles is written by : Nermeen Nabil Khear Abdelmalak
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