On September 28, 2024, the decentralized finance ecosystem suffered one of its most devastating single-wallet attacks of the quarter when a prominent crypto whale lost over $32 million worth of Spark Wrapped Ethereum (spWETH) tokens after signing a malicious permit signature. The incident, tracked by blockchain security firm Scam Sniffer, saw approximately 12,083 spWETH tokens drained from the victim’s wallet in a matter of seconds, with the attacker swiftly distributing the stolen assets across five separate wallets to obscure the trail.
The Exploit Mechanics
The attack hinged on a deceptively simple but devastatingly effective technique: permit phishing. Unlike traditional transactions that require gas fees and visible on-chain activity, permit signatures allow a third party to spend tokens on behalf of the owner. When the victim signed what appeared to be a routine transaction, they unknowingly granted the attacker unlimited approval to transfer their spWETH holdings. The attacker initially moved 10,000 spWETH to a primary wallet before distributing the remaining tokens across four additional addresses. This fragmentation strategy is a hallmark of sophisticated phishing operations, designed to complicate blockchain tracing efforts and delay any potential recovery.
The permit signature exploit is particularly insidious because it does not trigger the same mental alarms as a standard transaction. Users accustomed to approving token spends for legitimate DeFi protocols may not scrutinize the specific parameters of each signature request, especially when the prompt appears within a familiar interface or follows a phishing link that closely mimics a trusted platform.
Affected Systems
This attack was part of a broader wave of phishing incidents that plagued the crypto ecosystem throughout September 2024. According to Scam Sniffer’s monthly report, 10,805 victims collectively lost $46.7 million to various crypto phishing scams during the month. The total for the third quarter reached $126 million, with an average of 11,000 victims per month. Two major incidents alone accounted for $87 million of these losses. In a separate but related attack on the same day, another victim lost approximately $1 million after copying a poisoned address from a contaminated transaction history. The victim had successfully sent 200 ETH to the correct address earlier, but when attempting a follow-up transfer, they inadvertently copied an address inserted by the attacker, resulting in the loss of 410 ETH valued at roughly $1.1 million.
The primary vectors for these attacks were identified as fake accounts on X (formerly Twitter) and malicious Google advertisements, both of which directed victims to convincing phishing websites. Blockchain analytics firm MistTrack confirmed that the majority of victims were lured through these channels, underscoring the growing sophistication of social engineering campaigns targeting crypto users.
The Mitigation Strategy
In response to the escalating threat, security experts have emphasized several critical defensive measures. First and foremost, users should never sign permit signatures from unverified sources. Tools like Revoke.cash and Scam Sniffer’s browser extension can help users review and revoke unnecessary token approvals before they can be exploited. Hardware wallets such as Ledger provide an additional layer of protection by requiring physical confirmation of transaction details on the device screen, making it significantly harder for malicious signatures to be executed without the user’s explicit consent.
Yu Xian, founder of blockchain security firm SlowMist, commented on the persistent nature of phishing threats, noting that despite increased security education and improved defensive tools, phishing remains a significant headache for the ecosystem, often proving more damaging than advanced technical attack methods. His assessment highlights a fundamental challenge in crypto security: the human element remains the weakest link regardless of how sophisticated the underlying technology becomes.
Lessons Learned
The September 28 attack serves as a stark reminder that no wallet size is immune to social engineering. Whales holding tens of millions of dollars in assets can fall victim to the same fundamental tactics that ensnare newcomers. Key takeaways include always verifying the URL of any platform requesting a signature, using hardware wallets for high-value holdings, regularly auditing token approvals through revocation tools, and treating every signature request with the same caution as a wire transfer. The fact that this $32 million heist occurred through a simple permit signature rather than a complex smart contract vulnerability demonstrates that attackers are increasingly targeting user behavior rather than code.
User Action Required
If you hold significant crypto assets, take immediate steps to audit your existing token approvals. Visit Revoke.cash or use Scam Sniffer’s extension to review all active permissions on your wallets. Revoke any approvals you do not explicitly recognize or need. Consider migrating high-value holdings to a hardware wallet if you have not already done so. With Bitcoin trading at approximately $65,887 and Ethereum at $2,677 on this date, the stakes of poor security hygiene have never been higher. The next phishing link you click could be the one that empties your wallet.
Disclaimer: This article is for informational purposes only and does not constitute financial or security advice. Always conduct your own research and consult with security professionals before making decisions about your digital assets.
32m gone from signing one permit. if you hold that much in a single wallet you should be using a multisig period
single wallet with 12k ETH worth of spWETH and no multisig. at some point this is on the holder too
trashpanda77 exactly. 12,083 spWETH in a single wallet without multisig or timelock. at that level you need hardware wallet signing at minimum
splitting across 5 wallets is standard laundering but it still amazes me how fast they move. like clockwork
^ the speed is what gets me. seconds to drain, minutes to disperse. no undo button in crypto
the undo button problem is real. tradfi has chargebacks and disputes. crypto has irreversible transactions and hope
permit phishing is becoming the dominant attack vector and most wallet ux still makes signing look harmless. this is a ui problem as much as a user problem
the permit signature exploit is so clean from the attackers perspective. no gas cost, instant execution, and most users cant tell a malicious permit from a legitimate one