Approve, Allowance, Revoke: How Not to Turn Your Wallet Into an ATM

Disclaimer: this material is for informational purposes only and is not investment advice.

If tokens ever left your wallet without a confirmation, in 9 cases out of 10 it wasn’t a blockchain hack — it was an old permission you granted to a smart contract at some point. In 2026 this is one of the most common ways retail users lose funds: drainers, phishing pages, fake eligibility checks — the whole ecosystem revolves around signatures and token permissions.

Let’s break down what approve/allowance is, why unlimited approvals are dangerous, how revoke works, and what to do if you already clicked the wrong thing.

Key Terms

Approve: permission you give a smart contract to spend your tokens.

Allowance: the size of that permission (how much it can spend).

Revoke: cancelling that permission (usually setting allowance to zero).

You are not approving “your wallet”. You are approving a specific contract address — and often for a very large amount (sometimes effectively unlimited).

How Theft via Approve Usually Happens

A classic flow looks like this:

1. You land on a site: “airdrop / claim / check eligibility / mint / verify wallet”.
2. You connect your wallet.
3. The site asks you to do a “harmless” action — most often an approve.
4. You confirm it.
5. After that, the contract (or whoever controls it) can transfer your tokens without asking you again, until the allowance is revoked or exhausted.

That’s why it feels like tokens were taken without a signature. The signature happened — just earlier.

Why Unlimited Approval Is the Biggest Red Flag

Many interfaces default to max/unlimited so you don’t pay gas every time you swap or interact.

Upside: less friction.

Downside: one mistake can let someone drain your tokens to zero.

A practical rule:

• For one-off actions, approve an exact amount (or a small cap).
• Unlimited approvals should be treated like giving a company your card with no spending limit.

2026’s Extra Risk: Permit/Permit2 and Gasless Signatures

This is where many users get caught. 

There are two different realities:

1) Classic ERC-20 approve

This is an on-chain transaction. You pay gas. The approval is visible in explorers and in revoke tools.

2) Permit / Permit2 (gasless permissions via signatures)

Here you sign a message, and the ability to spend tokens can be activated via a different mechanism (sometimes without you sending a separate approval transaction at the moment of signing). 

For the user it’s worse: “just a signature” → tokens gone.

If a site asks you to sign to verify or sign to check eligibility, treat it as high risk. In many real scams, that is the whole attack.

How to Check Which Contracts Have Permissions

Pick any one of these approaches.

Option A: Revoke tools

Open a token approval checker, connect your wallet, select the network, and review approvals.

What to look for:

• unfamiliar contract names/domains;
• huge allowances;
• allowances for stablecoins (USDT/USDC/DAI) — a drainer favourite;
• NFT approvals (often shown in a separate tab).

Option B: Blockchain explorers (Etherscan and equivalents)

Good if you want to verify addresses manually.

What to look for:

• Approve transactions;
• the contract address that received the allowance;
• token approval lists (if the explorer UI provides them).

Option C: Your wallet interface

Some wallets show approvals, but specialised tools are usually faster and clearer.

How to Revoke Safely 

Step 1: Identify the correct network

Approvals are per network: Ethereum, Arbitrum, Base, BNB Chain, etc.

If you approved during a claim on one chain — you must revoke on that same chain.

Step 2: Pull up approvals and prioritise by risk

Start with stablecoins (USDT/USDC/DAI), large liquid tokens (wrapped ETH, major assets), everything else.

Step 3: Remove unlimited and unknown approvals

Use Revoke/Set allowance to 0.

This is usually an on-chain transaction, so you will pay gas.

Step 4: Re-check after a few minutes

Some interfaces cache results. Confirm the allowance is now 0.

What to Do If Tokens Were Already Drained

Treat it like a fire.

1) Move remaining assets to a new address — immediately

• ideally create it in a clean browser profile or device;
• don’t connect the compromised wallet to any “recovery” or “check” sites.

2) Revoke approvals on the compromised address

This won’t recover stolen funds, but it can stop further transfers of anything still left.

3) Check approvals across all networks

Scams are often multi-chain. People clean Ethereum and forget Base/Arbitrum.

4) Separate “risk activity” from your main wallet going forward

If that address was used for airdrops/mini-apps, don’t keep using it as your primary wallet.

Conclusion

Approve is a useful mechanic — and also the reason wallets most often become an ATM for attackers. In 2026 the winners are the people who run basic hygiene: limit approvals, revoke regularly, and separate addresses by role.