Drainer Signatures: What You Are Approving

A wallet drainer rarely breaks encryption. It asks you to authorise something, then uses the authorisation exactly as written. The signature is valid, the contract behaves as coded, and the loss appears on-chain as a transfer you permitted. That is why a wallet drainer is better understood as a permissions problem than a cryptography problem.

The distinction changes what defence looks like. You cannot audit your way out of a signature you have already given, but you can read what a request is asking for before you approve it, and you can withdraw permissions you no longer need.

• A drainer is a permission request, not an exploit. Nothing is broken; something is granted.
• Approvals outlive the site that asked for them. The permission sits on-chain, not in a browser tab.
• Permit signatures skip the approval step entirely. No on-chain transaction means nothing to revoke afterwards.
• Revocation is cheap and tedious. It is the only reliable cleanup once a permission exists.

What a wallet drainer asks you to sign

Almost every drainer interaction resolves into one of four request types. They differ in scope and in whether you can undo them later, which is the part most interfaces hide.

Token spending approval

This grants a contract permission to move a specific token up to a specific amount. The field that matters is the spender, not the token. A request to approve a token you recognise tells you nothing if the spender is an address you have never seen.

Unlimited approvals are the default on many interfaces because they save gas on later trades. They also mean the permission has no ceiling, and the contract keeps it until you reset it.

Collection-wide approval

For NFTs, a single approval can cover an entire collection rather than one item. Approving one piece can therefore expose every piece you hold from that collection, including ones minted after the approval was signed.

Off-chain permit signatures

A permit is a signed message rather than a transaction. It costs no gas, which is exactly why it appears in phishing flows: there is no gas estimate, no on-chain confirmation screen, and no transaction to inspect afterwards. If the permit is later submitted, the transfer happens without you pressing anything again.

Opaque payloads and blind signing

Some requests arrive as raw bytes that your wallet cannot decode. The wallet can only show a hash. Approving a hash is not approval of anything you can describe, and a signature over an unreadable payload should be treated as a signature over an unknown instruction.

Why a wallet drainer request looks ordinary

These requests use the same standards as legitimate applications, so the wallet has no reason to flag them. The transaction is well-formed. The contract is deployed and verified. The interface may be a convincing copy of one you already use.

The weak point is the summary line. Wallets compress a request into a short sentence, and that sentence often omits the spender, the amount, or both. The detail exists one tap deeper, in a panel most people never open. A drainer depends on that habit.

There is also a timing component. Requests arrive when you are mid-task: claiming a reward, minting, migrating a position. Attention is on the outcome you want, not on the fields in front of you. Anything that adds friction to that moment, such as a second device or a written checklist, is worth more than another article read after the fact.

Treat every signature as a contract with a stranger. The question is not whether the site looks trustworthy, but what the signature would let the other party do tomorrow, after the site has disappeared.

Comparing the request types

How to check a request before signing

Reading a request takes about thirty seconds once you know which fields to look at. The order below is deliberate: address first, because everything after it is meaningless if the target is wrong.

1. Open the full detail view, not the one-line summary.
2. Copy the contract address and compare it against the address published by the project you intended to use.
3. Read the function name. Approval, permit, transfer and batch transfer are four different commitments.
4. Find the spender field and confirm it is the contract you expect, not an arbitrary address.
5. Check the amount. If it is unlimited and you did not intend a long-term position, reduce it.
6. Check the deadline on any permit. A long or absent expiry extends the window for it to be used.
7. If any field is unreadable on your device, decline. A hardware screen showing a hash is not a review.

Reducing what a wallet drainer can reach

Separate wallets do more than any single habit. Keep a small hot wallet for new sites and a holding wallet that never connects to anything unfamiliar. A drainer can only take what the wallet it reached was allowed to move.

Review existing approvals periodically, particularly after using a new application. Most explorers and several independent tools list outstanding allowances by wallet, and revocation is a normal transaction. It costs a fee, and on some networks that fee is the only friction.

Hardware wallets help only when the screen shows the amount and the recipient. If the device displays a hash, it has reduced a signing decision to a confirmation, which is a weaker guarantee than it appears.

One more limit is worth stating plainly. No amount of approval hygiene protects a key that has been copied. A signature is only as safe as the device that produced it, and a phrase typed into a website, a browser extension or a screenshot folder is outside every control described here.