A cryptocurrency user lost nearly 1 million USD Coin (USDC) due to mistakenly signing a malicious contract 458 days ago, indicating that the tactic of waiting out long periods before exploiting contracts is becoming more common.
Experts warn that not regularly reviewing and revoking old contract approvals on e-wallets can create vulnerabilities, allowing hackers to wait for the opportunity to withdraw all assets from victims after many months or years.
MAIN CONTENT
Exploiting old contracts caused users to lose 908,551 USD USDC after more than 15 months since the approval occurred.
The trend of scamming by signing contracts and then waiting for the right moment to attack is on the rise, deceiving even experienced users.
Experts recommend checking and revoking old approvals of wallets to protect assets against increasingly sophisticated scams.
How did this user lose 908,551 USD USDC?
A cryptocurrency user lost a total of 908,551 USD USDC after being exploited by a malicious contract approval signed over 15 months ago. This incident exposes the potential risks of not controlling old contract approvals on e-wallets.
On-chain data shows that the victim signed approval for a malicious Smart Contract on April 30, 2024, possibly through a fake Airdrop program or accessing a fake exchange site. By the morning of August 2, 2025, hackers had withdrawn nearly the entire USDC balance of the victim after almost 16 months of waiting.
It is noteworthy that hackers do not attack immediately after the victim signs the contract but silently wait for a long time to deceive alertness while monitoring large fund transfer movements on the target wallet. This strategy is becoming increasingly popular as cybercriminals in the cryptocurrency field adopt patient techniques, studying user behavior before striking.
"Regularly checking and revoking old approvals is extremely important for your wallet security!"
Scam Sniffer, scam detection team on X, August – 2025 (source: X/@realScamSniffer)
Why are old contract approvals dangerous?
On-chain analysis shows that the attack originated from an ERC-20 standard approval allowing the scammer wallet address (0x67E5Ae, linked to pink-drainer.eth) full access to Tokens without needing to reconfirm with the victim.
The major risk lies in the fact that this malicious Smart Contract grants permanent Token control until manually revoked on the wallet. According to Scam Sniffer's report, hackers patiently waited for up to 458 days from the moment the victim signed the approval before executing the USDC withdrawal.
Notably, before being attacked, the victim's wallet only had small low-value transactions to avoid attracting attention from automatic scam detection systems, indicating the hackers' sophisticated hiding tricks.
What turning point led to this major attack?
A notable development occurred on July 2, when the victim transferred 762,397 USD USDC from MetaMask to a new wallet (0x6c0eB6) at 20:41 Vietnam time, and then added another 146,154 USD USDC just 10 minutes later from a Kraken account.
These large movements are publicly displayed on the Blockchain, likely coming under the hackers' radar. However, instead of acting immediately, the attackers continued to monitor for an additional month to ensure there were no transaction reversals or additional asset deposits.
At 4:57 AM on August 2 (Vietnam time), the hacker finally executed the command to withdraw all remaining USDC, immediately transferring it to a wallet labeled Fake_Phishing322880, which was later flagged by Scam Sniffer as a scam address.
"Today's cryptocurrency attacks are no longer spontaneous but increasingly sophisticated, patient, and pursuing long-term targets."
Galaxy Research Report, 2025 (source: galaxy.com/insights)
What vulnerabilities have hackers exploited from old contract approvals?
Hackers exploit on-chain characteristics, as ERC-20 approvals exist permanently unless manually revoked using tools like Etherscan or wallet approval management services. The victim's complacency, not checking the signed contract creates opportunities for hackers to access wallets anytime.
In many cases, victims signed approvals through unverified Airdrop programs, fake websites, or services requiring wallet connections that then redirected to dangerous Smart Contracts. After signing approvals, all safety is merely temporary until the attacker strikes.
Experts like Scam Sniffer recommend that users should use contract approval tracking tools to detect risks and revoke Token access from services that are no longer in use to minimize the risk of asset loss.
"Today's attackers do not only rely on automated tools, but also closely monitor every move of their victims, even those wallets that only perform small activities to avoid detection."
Scam Sniffer Report, August – 2025 (source: scam-sniffer.io)
Why are malicious contract fraud schemes becoming more sophisticated?
Fraud in the cryptocurrency industry continues to evolve in a less predictable direction, leveraging new technology, a lack of vigilance, and users' habit of trusting popular services.
Many cases of using deepfake AI impersonating leaders of large companies like Ripple, or impersonating YouTube channels with hundreds of thousands of followers to launch fake XRP giveaway events have deceived many investors, both new and experienced.
The emergence of a massive leak of login information up to 16 billion records complicates security issues further. According to Galaxy Research, sophisticated phishing attacks, combined with a sense of urgency, impersonation, and cross-platform manipulation can deceive even seasoned cybersecurity experts.
Fact: Even experts fall victim to new scams.
Many real cases have recorded security analysts, even security experts like Christopher Rosa, falling victim to phishing attacks through impersonated emails, fake Coinbase calls, and closely coordinated social engineering scams.
The nature of these attacks is to exploit the psychology of complacency, overconfidence, and the complexity of current DeFi platforms. Therefore, the core perspective is that old approvals on wallets never expire, and hackers never forget their 'prey'.
"Old approvals do not expire by themselves. And hackers never forget high-value targets even after a long time."
Security expert Christopher Rosa, August – 2025 (source: Galaxy/AMBcrypto)
How to avoid malicious smart contract scams?
To minimize the risk of becoming a victim of malicious contract attacks, experts advise users to regularly check, review, and revoke approvals granting access to Tokens on wallets.
Tools like Revokecash, Etherscan Token Approval Checker, or approval management applications from major wallets can be used to control access and eliminate dangerous contracts. At the same time, one should increase vigilance when receiving Airdrop offers, accessing websites/exchanges of unverified origins.
Storing large amounts of money in cold wallets, avoiding keeping all assets on hot wallets also helps to prevent the risk of being completely drained during the period hackers wait for the opportunity to execute withdrawal commands on approved contracts.
Compare the risk levels between cryptocurrency storage and trading channels
Storage/transaction form Risk of exploiting old contracts Security potential Hot wallet (MetaMask, Trust Wallet…) High, due to frequent approvals and vulnerability to phishing User awareness dependent, needs regular contract checking Cold wallet (Ledger, Trezor…) Low, almost impossible to exploit if not online Very high, unless under physical attack or exposure of Private Key CEX exchange Medium, primarily risk if access information is exposed Security at the exchange level, but risk from the exchange itself or internal scams DApp/DeFi High, risk from unverified contracts, fake interfaces User skills and project reliability dependent
Risks from abusing Airdrop programs, fake websites
One of the reasons victims mistakenly sign malicious contracts is due to participating in unverified Airdrops or logging into websites resembling popular exchanges. Fake sites often require users to connect wallets, grant 'Approve' Token permissions, or sign messages – this is the gateway for hackers to set traps.
Scam Sniffer advises always checking the validity of programs, verifying links, and thoroughly checking smart contract agreements before signing on wallets. Do not keep large assets on wallets that have registered for many Airdrop services or projects inviting 'free' offers.
Additionally, personal data leaks, login information… are also sources of information that help hackers easily identify wallets and emails for multi-layered fraud.
The practical impact of old contract scams on the community
Incidents like the loss of 908,551 USD USDC mentioned above further increase distrust in DeFi platforms, while also demanding the industry to enhance protection tools and alert users.
According to Galaxy Research, in 2025, the number of old contract scams and phishing related to major wallets increased sharply, with losses in many cases reaching millions of USD. Victims are becoming increasingly diverse in experience, even developers and platform administrators have fallen into the sights of cybercriminals.
Educating the community about contract safety and personal skills to control approvals is currently the most encouraged proactive solution to prevent wallet withdrawals after many months/years of 'hibernation'.
Enhanced measures to prevent malicious contract scams
In addition to monitoring and revoking approvals, security experts recommend that users should use separate wallets for trading and storage, only connecting small-volume wallets to new DApps/websites or unverified projects.
Should apply additional layers of protection such as two-factor authentication (2FA), phishing alerts from wallets, and contract checks on explorers before signing commands. Additionally, splitting assets across multiple wallets, not putting 'all eggs in one basket' remains a basic but effective risk management strategy.
DeFi projects also need to strengthen contract audits, transparently disclose risks, and update interfaces to alert users as soon as connecting wallets or signing approvals.
Frequently asked questions
How to check and revoke contract approvals on the wallet?
Use tools like Revoke.cash, Etherscan Approval Checker, or major wallet management apps to review and revoke unused contracts. It should be done regularly every month or after participating in new projects.
Why do old contract approvals pose such a great risk?
ERC-20 approvals exist indefinitely until revoked, hackers can wait a long time to observe wallets transferring many assets before withdrawing everything when you let your guard down.
Can I be safe if I only use a cold wallet for storage?
Cold wallets are very secure, as long as they are not connected online or share the Private Key. However, it is still important to ensure that no permissions are granted when transferring assets from cold wallets to hot wallets.
What to do when asset leakage is detected through a malicious contract?
Immediately revoke approvals on all Tokens, transfer remaining assets to a new wallet, change the Private Key if there are signs of information leakage, and report to reputable scam detection teams.
Are contracts of large projects absolutely safe?
No, even large projects can have vulnerabilities or be exploited if users are complacent, approving from fake channels or sites. Always check the origin carefully before approving.
How do hackers know when to withdraw money?
Hackers monitor on-chain, large fund transfers, unusual wallet activities on the Blockchain to choose the right timing, avoiding detection when acting.
What is the most effective preventive solution today?
Regularly checking and revoking approvals, not connecting wallets on unverified sites, splitting assets, using cold wallets, and updating security alerts from experts are the best solutions.
Source: https://tintucbitcoin.com/usdc-bi-danh-cap-canh-bao-vi/
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