If you have been following cryptocurrency news in early June 2025, you have probably seen headlines about major DeFi protocols losing hundreds of millions of dollars to hackers. The Cetus Protocol on Sui lost approximately $223 million on May 22, and ALEX Protocol on Stacks lost about $8.3 million on June 6. These numbers can be alarming, especially if you are new to decentralized finance. Understanding what happens after a hack — and what you can do about it — is essential knowledge for anyone participating in DeFi. With Bitcoin trading near $105,793 and the crypto market cap exceeding $3.4 trillion, DeFi is not going away, so learning how to navigate its risks is time well spent.
The Basics
When we say a DeFi protocol was hacked, we mean that someone found a flaw in the protocol’s smart contract code — the self-executing programs that run on the blockchain — and used that flaw to drain funds from the protocol’s liquidity pools or user deposits. Unlike a traditional bank robbery, there are no physical vaults or security guards. Everything happens through code, and because blockchain transactions are irreversible, stolen funds cannot simply be reversed by calling the bank.
DeFi hacks typically fall into several categories. Flash loan attacks exploit the ability to borrow massive amounts of cryptocurrency without collateral for a single transaction. Logic vulnerabilities, like the one that hit ALEX Protocol, exploit flaws in how the protocol processes certain operations. Bridge exploits target the mechanisms that move assets between different blockchains. Oracle manipulation attacks feed false price data to protocols that rely on external price feeds.
Why It Matters
Understanding DeFi hacks matters because your money is at stake. When you deposit funds into a DeFi protocol — whether to earn yield, provide liquidity, or trade — you are trusting that the protocol’s code is secure. Unlike traditional finance, where banks and regulators provide safety nets like deposit insurance, DeFi operates on a code-is-law philosophy where users bear the risk directly. The total amount lost to crypto hacks in 2025 exceeded $2.2 billion, making security awareness not optional but essential for anyone putting real money into these protocols.
The good news is that the DeFi ecosystem has developed increasingly sophisticated recovery mechanisms. Many protocols now maintain insurance funds, conduct regular security audits, and have formal incident response procedures that can partially or fully reimburse affected users.
Getting Started Guide
If a protocol you are using gets hacked, the first step is to disconnect your wallet from the compromised protocol immediately. Use tools like Revoke.cash or Etherscan’s token approval checker to revoke any outstanding token approvals you have granted to the affected protocol. This prevents the attacker from using previously granted permissions to access your remaining funds.
Next, monitor the protocol’s official communication channels. Legitimate protocols will post updates through their official X accounts, Discord servers, and governance forums. Be extremely cautious of direct messages claiming to offer recovery assistance — scammers frequently target hack victims with phishing links disguised as claim portals. Always verify that communications come from verified official accounts.
When a protocol announces a reimbursement plan, follow the claim instructions carefully. ALEX Protocol, for example, sent on-chain claim notifications to affected wallets and required users to submit claim forms by a specific deadline. Reimbursements were calculated based on average exchange rates at the time of the exploit. Cetus Protocol relaunched on June 8 after conducting full security audits and recovering the majority of stolen funds, allowing users to access their restored positions.
Common Pitfalls
The biggest mistake new DeFi users make is panic selling or rushing to withdraw funds without understanding the situation. During a hack, blockchain networks can become congested, driving gas fees to extreme levels. Blindly rushing to move funds can result in paying hundreds of dollars in transaction fees for actions that may not even be necessary if the protocol has a reimbursement plan in place.
Another common pitfall is trusting unofficial recovery channels. After every major hack, scammers create fake websites, social media accounts, and Telegram groups claiming to help victims recover their funds. These are always scams. Legitimate recovery processes are communicated exclusively through official protocol channels and typically involve on-chain claim mechanisms rather than forms on unfamiliar websites.
Failing to diversify across protocols is perhaps the most preventable pitfall. Putting all your DeFi capital into a single protocol means a single hack can wipe out your entire position. Spreading funds across multiple well-audited protocols limits your exposure to any single point of failure.
Next Steps
To protect yourself going forward, make a habit of checking a protocol’s audit history before depositing funds. Look for audits from reputable firms like Trail of Bits, OpenZeppelin, or CertiK. Monitor the protocol’s bug bounty program — well-funded bounty programs attract skilled security researchers who find vulnerabilities before attackers do. Consider using DeFi insurance protocols like Nexus Mutual or InsurAce to purchase coverage against smart contract exploits. And always, only invest what you can afford to lose in any single protocol.
The Cetus and ALEX incidents of June 2025 are reminders that DeFi remains an evolving, high-risk environment. But with proper precautions and a clear understanding of recovery processes, you can participate in decentralized finance with your eyes open to the risks and a plan for responding when things go wrong.
Disclaimer: This article is for educational purposes only and does not constitute financial or investment advice. Always conduct your own research before engaging with any DeFi protocol.
AMM innovations like concentrated liquidity changed everything
defi_miner_ Cetus losing 223M and ALEX losing 8.3M in the same month. the scale of these exploits is accelerating not slowing
the Cetus exploit on Sui was especially rough because that chain was supposed to have better security guarantees than EVM alternatives. turned out Move language has its own class of bugs
rekt_prepper Move was supposed to be the safe alternative and Cetus still got hit. the language helps but it doesnt make audits optional
lost 3 ETH on a bridge exploit last year and the recovery process described here is basically what i went through. insurance on DeFi protocols is a joke right now
rekt_anon which bridge got you? took me 3 months to get tx history together for the insurance claim and still got back 11 cents on the dollar
insurance paying 11 cents on the dollar after the bridge claim process is insulting. 4 months of paperwork for basically nothing
Cross-chain DeFi is the next frontier
Real yield protocols are separating from the Ponzi-nomics era
DeFi yields are finally sustainable without token emissions
the section about getting your tx history for insurance claims is actually useful. most guides skip the bureaucratic side of getting hacked
the $223M Cetus drain happening on Sui of all chains was wild. Move language was supposed to prevent exactly these overflow bugs. guess formal verification isnt a silver bullet
Linnea F. the irony is Move was supposed to prevent exactly the Cetus style exploit. resource oriented design helps but auditors still need to actually use the borrow checker properly
Linnea F. Move was supposed to prevent overflow bugs but Cetus showed that the borrow checker is only as good as the human writing the code
flash loan attacks are the most fascinating exploit category. borrow millions with zero collateral, drain a pool, repay in one transaction
flash loans let anyone become an attacker with zero capital. the barrier to entry for exploits dropped to basically zero because of them
Kwame Asante flash loans dropped the barrier to zero but oracles are still the weak link. if your price feed is manipulable the rest of the stack doesnt matter
flashloan_rat_ oracles are the entry point but the real issue is protocol design that allows flash loan manipulation in the first place. Cetus lost 223M because the math was exploitable
beginner guide is generous. this is more intermediate. but the checklists at the end are worth bookmarking
the insurance claim process took me 4 months after a bridge exploit. most people give up before finishing the paperwork. that should be in the guide
Mihai C. 4 months for an insurance claim is insane. traditional fintech resolves disputes in days not months. DeFi needs to fix this gap
Mihai C. 4 months for an insurance claim is insane. traditional banking disputes get resolved in weeks. DeFi still has no real consumer protection layer