The Hidden Threat of "Infinite Approvals"
When swapping tokens on decentralized exchanges (Uniswap, SushiSwap) or staking on DeFi yield farms, user interfaces prompt you to approve token spending. To save users from paying gas on future trades, dApps traditionally requested "Unlimited / Infinite Approvals" (type(uint256).max).
How Cybercriminals Exploit Stale Allowances
Even after you disconnect your wallet and delete browser history, smart contract allowances remain permanently recorded on the blockchain:
- Protocol Exploits: If a DeFi protocol smart contract is exploited months later, the attacker can execute
transferFrom()calls to drain approved tokens directly from connected user wallets. - Phishing Permit Signatures: Malicious phishing frontends trick users into signing off-chain EIP-2612 Permit signatures, instantly transferring token allowances to a drainer address without paying gas.
Essential Wallet Sanitization Protocol
- Visit trusted allowance auditing platforms like Revoke.cash or Etherscan Token Approvals.
- Filter for unlimited approvals on high-value stablecoins (USDT, USDC, DAI) and revoke all allowances for unused protocols.
- When approving new trades, set Exact Spending Caps equal only to the specific transaction amount rather than default unlimited allowances.
Read our investigation on signature poisoning and permit2 drainer exploits.
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