Token Approval Safety: How to Revoke Dangerous Approvals

Token approvals are one of the most common attack vectors in crypto. When you approve a token, you're giving a smart contract permission to spend your tokens. If that contract is malicious, it can drain your entire balance.

How Token Approvals Work

ERC-20 tokens have two approval functions:

• approve(address spender, uint256 amount) — Grants a specific amount to a spender
• increaseAllowance(address spender, uint256 addedValue) — Increases existing allowance

The dangerous pattern is approving type(uint256).max (unlimited approval). This gives the spender permission to transfer ALL your tokens at any time.

Why Unlimited Approvals Are Dangerous

Many dApps request unlimited approvals for convenience. But this creates a permanent security risk:

• If the dApp contract is compromised, attackers can drain your tokens
• If you interact with a phishing site, the approval persists
• Approvals remain active even after you stop using a dApp
• No notification when approved tokens are spent

How to Check Your Approvals

Regular approval audits are essential:

1. Use Etherscan's Token Approval Checker for each chain
2. Use SweepGuard's approval scanner for multi-chain auditing
3. Check both ERC-20 and ERC-721 (NFT) approvals
4. Revoke any approvals you no longer need

Best Practices

• Only approve the exact amount you need
• Revoke approvals after using a dApp
• Never approve tokens on unfamiliar sites
• Use SweepGuard extension to get warnings before signing
• Audit approvals monthly across all chains