The July 1, 2023 Poly Network exploit that minted $34 to $42 billion in fraudulent tokens across 10 blockchains highlights a critical but often overlooked aspect of DeFi security: token approval hygiene. While most discussions focus on the bridge vulnerability itself, the secondary risk to users comes from standing token approvals — permissions granted to smart contracts that allow them to spend tokens from your wallet indefinitely. This advanced tutorial walks you through systematically auditing and revoking dangerous approvals across Ethereum, BNB Chain, Polygon, and other EVM-compatible networks. With Bitcoin at $30,590 and Ethereum at $1,924, the value at risk from neglected approvals has never been higher.
The Objective
Every time you interact with a DeFi protocol — whether swapping tokens on Uniswap, providing liquidity to a bridge, or depositing into a lending protocol — you grant a smart contract permission to spend specific tokens from your wallet. This permission, called a token approval or allowance, is stored on-chain and persists until explicitly revoked. The problem is that most users accumulate dozens or hundreds of these approvals over time, many of which point to contracts they no longer use or protocols that may have been compromised since the approval was granted.
The objective of this tutorial is to conduct a comprehensive audit of all active token approvals across every blockchain where you hold assets, identify and categorize the risk level of each approval, and revoke any that are unnecessary or dangerous. This is not a theoretical exercise — after the Poly Network hack, several security firms reported that users with active approvals on affected contracts faced elevated risk of secondary exploitation.
Prerequisites
Before starting this audit, ensure you have the following tools and information ready. You need access to your wallet addresses on each blockchain you use. For MetaMask users, this is simply your Ethereum address and any EVM-compatible addresses on other chains. You need a web browser with MetaMask or another Web3 wallet extension installed. You should have a small amount of native tokens on each chain to cover gas fees for revoking approvals — typically 0.001 to 0.01 ETH, BNB, or MATIC per revocation.
Familiarize yourself with Etherscan, BscScan, and PolygonScan, as you will use these block explorers to verify approval details. Install the Revoke.cash browser extension or bookmark the website for streamlined approval management. Finally, prepare a spreadsheet or text document to track your findings — systematic documentation is essential for a thorough audit.
Step-by-Step Walkthrough
Step 1: Inventory Your Wallets and Chains
Begin by listing every wallet address and every blockchain where you have active positions. For most DeFi users, this includes Ethereum mainnet, BNB Chain, Polygon, Arbitrum, Optimism, and Avalanche. Connect each wallet to Revoke.cash and select the appropriate network from the dropdown menu. The tool will display all active token approvals for the connected address on the selected chain.
Step 2: Categorize Approvals by Risk Level
For each approval, assess its risk level using three criteria. First, check whether the approved contract is associated with an active, well-maintained protocol. If the protocol has been deprecated, hacked, or migrated to new contracts, the approval is high risk. Second, examine the approval amount. Approvals set to unlimited (represented as a very large number like 115792089237316195423570985008687907853269984665640564039457584007913129639935) are standard practice but represent maximum exposure if the contract is compromised. Third, verify whether the approved token still has significant value. Approvals for worthless tokens are low priority but should still be revoked for cleanliness.
Step 3: Cross-Reference With Known Vulnerabilities
After the Poly Network exploit, check whether any of your approvals point to Poly Network contracts or contracts of protocols that integrated with Poly Network. Security firms including PeckShield and Beosin published lists of affected contract addresses following the July 1 attack. Compare these addresses against your active approvals. Any matches should be revoked immediately regardless of their other risk characteristics.
Use the Contract Reader tool on Etherscan or BscScan to examine each approved contract. Look for the contract’s verification status, creation date, and whether it has been flagged by security scanners. Unverified contracts or those created recently should be treated with maximum suspicion.
Step 4: Execute Revocations
For each approval you have determined should be revoked, use Revoke.cash to execute the revocation transaction. The process involves clicking the revoke button next to the approval, confirming the transaction in your wallet, and paying a small gas fee. On Ethereum mainnet, gas costs for approval revocations typically range from 15,000 to 30,000 gas units, which at current gas prices translates to approximately $1 to $5 per revocation.
For bulk revocations, consider using the batch functionality available on some approval management tools. This allows you to revoke multiple approvals in a single transaction, saving gas fees and time. However, be aware that batch transactions have higher gas limits and may fail if any individual revocation encounters an error.
Step 5: Verify and Document
After revoking approvals, refresh Revoke.cash or check the relevant block explorer to confirm that the approval has been successfully removed. Document every revocation in your tracking spreadsheet, including the contract address, token, approval amount, revocation transaction hash, and date. This documentation serves as both an audit trail and a reference for future security reviews.
Troubleshooting
If you encounter a revocation transaction that consistently fails, several issues may be responsible. First, the gas limit may be too low — try manually increasing the gas limit to 50,000 or higher in your wallet’s advanced transaction settings. Second, the contract may have a non-standard approval interface that standard tools do not handle correctly — in this case, you will need to interact with the contract directly through Etherscan’s Write Contract function, calling the approve function with the spender address and an amount of zero.
If Revoke.cash shows approvals that do not appear on the block explorer, you may be seeing cached data. Clear your browser cache and reconnect your wallet. Conversely, if approvals appear on the block explorer but not in management tools, the tool may not support that specific token standard — use the block explorer directly to revoke.
For hardware wallet users, revocation requires the same signing process as any other transaction. Ensure your device is connected, unlocked, and running the latest firmware. If you use a Ledger with MetaMask, enable Blind Signing in the Ledger Ethereum app settings to approve revocation transactions.
Mastering the Skill
Effective token approval management is an ongoing discipline, not a one-time task. Establish a regular approval audit schedule — weekly for active DeFi users, biweekly for casual users. Every time you interact with a new protocol, note the approval in your tracking document. When you finish using a protocol, immediately revoke the associated approvals rather than leaving them for a future cleanup.
For maximum security, consider using dedicated wallet addresses for different protocol categories. One address for decentralized exchanges, another for lending protocols, and a third for bridging. This compartmentalization ensures that even if one approval is exploited, the blast radius is limited to the funds in that specific wallet. Combined with hardware wallet security for your primary holdings, this approach provides defense in depth that significantly reduces the risk of approval-based exploits — a lesson the Poly Network hack has driven home for the entire crypto community.
Disclaimer: This article is for informational purposes only and does not constitute financial or investment advice. Always conduct your own research before making any financial decisions.
the standing approval problem is the silent killer in defi. people wonder how their wallets get drained and its usually some dusty approval from 2 years ago
revoke.cash exists and does exactly this. the problem is most people dont know they need to use it until after they get rekt
revoke.cash is great but the poly network exploit was a bridge vuln not an approval issue. different attack vector entirely. good guide for awareness tho
revoke.cash handles it but doing it manually per chain on etherscan is how most people learn the hard way. batch revoke tools should be default
went through my own approvals last month. found 47 open permissions from protocols i havent touched since 2022. revoked all of them in one afternoon
found 47 open approvals from protocols that dont even exist anymore. some were for unlimited amounts. batch revoke should be a monthly habit like checking your credit card statement
revoking across multiple EVM chains is tedious but necessary. would love to see a tool that does it in one transaction batch
multi-chain batch revoke exists now on revoke.cash and a few others. the UX is still rough but beats doing arb, poly, base one by one
Poly Network minting 42B in fake tokens was the wake up call. but the real danger is the long tail of approvals to contracts with upgradeable proxy patterns that can be hijacked anytime