Token Approvals: The Hidden Risk in Your Wallet
Every DeFi interaction grants token approvals. Many users have unlimited approvals active on contracts they used once. How to audit your approvals and revoke risky permissions before they're exploited.
What Token Approvals Are
When you swap tokens on a DEX, you first sign an 'approve' transaction that gives the DEX's smart contract permission to move your tokens on your behalf. This is the ERC-20 approve() function -it says 'this contract can spend up to X amount of this token from my wallet.' Most DeFi interfaces request unlimited approval (the maximum possible value, 2^256 - 1) so you don't have to re-approve every time you swap. This is convenient, but it means the contract can move ALL of that token from your wallet at any time, without any further permission from you, until you explicitly revoke the approval.
The Exploit Vector
If a contract you've approved has a vulnerability, or if the contract is upgradeable and the team turns malicious, anyone who can call transferFrom on that contract can drain every approved token from your wallet. This has happened repeatedly: in 2023, a vulnerability in the Multichain bridge contract allowed attackers to drain tokens from users who had granted approvals years earlier. The users had long forgotten about the approval. They hadn't interacted with Multichain in months. But the unlimited approval was still active, and the attacker used it to take everything. This is not a rare edge case -approval-based drains account for a significant portion of DeFi losses.
Auditing Your Active Approvals
Go to revoke.cash and connect your wallet. It will scan all chains and show every active token approval: which contract, which token, and how much is approved. You will likely find dozens of approvals you've forgotten about -DEX routers, lending protocols, NFT marketplaces, bridge contracts. Each one is a potential attack surface. Etherscan also has a Token Approval Checker under More > Token Approvals. Sort by 'Approved Amount' to find unlimited approvals first -these are the highest risk. Review each one: do you still use this protocol? Is the contract verified and actively maintained? If not, revoke it.
Best Practices Going Forward
Approve the exact amount needed for each transaction, not unlimited. Most modern DeFi interfaces let you edit the approval amount before signing. Yes, you'll need to re-approve next time -that re-approval is a security feature, not an inconvenience. Revoke approvals after you're done with a protocol, especially for contracts you don't plan to use again. Use a hardware wallet for approval transactions -the physical confirmation step forces you to read what you're signing. Consider using a separate 'DeFi wallet' with limited funds for interacting with new or unaudited protocols, keeping your main holdings in a wallet that has never approved any contracts.