The claim button is theater. The signature prompt is the weapon.

Every industrial-scale airdrop theft follows the same shape: a polished page manufactures intent, and then a signature converts that intent into authorization. No seed phrase, no download, no transaction you watch leave your wallet. Just a “verify eligibility” prompt, a click, and a spending grant that the attacker exercises minutes or weeks later.

This guide compares the four signature types that matter in claim contexts — what each one actually authorizes, how drainer kits abuse them, and how to read the prompt before your thumb moves. For the surrounding picture, see how the biggest airdrop scams work and our general guide to crypto airdrop scams.

Why signatures beat seed phrases for attackers

Early crypto phishing went after recovery phrases. Modern drainers go after signatures, for three reasons:

  1. Signatures feel safe. Users have been trained that the seed phrase is sacred; they know not to type it into websites. But “connect and verify” feels like normal Web3 behavior.
  2. Connected wallets lower the guard. Once a wallet is connected and has signed one harmless message, the next prompt gets less scrutiny — social engineering via habituation.
  3. The theft is decoupled. With an approval in hand, the attacker can sweep when the balance grows or the heat dies down. You never see the outgoing transfer.

The result, per Scam Sniffer’s annual reports: hundreds of millions lost to wallet drainers in recent years, dominated by signature-based theft.

Signature type 1: the token approval

The classic. The claim flow asks your wallet to call approve() on an ERC-20 contract, granting a spender an allowance over your tokens.

  • What it authorizes: the spender (the drainer contract) to move up to the approved amount of that specific token.
  • How it is abused: the prompt shows “approve” with an allowance — frequently unlimited — and users confirm because they believe they are claiming. The attacker later calls transferFrom and takes the tokens.
  • How to read it: check the spender and the amount. If the allowance is unlimited and the site is unfamiliar, you are granting a blank check. See infinite approvals explained and token approval safety for the full picture, including how to revoke.

Signature type 2: the Permit2 approval

Permit2 is Uniswap’s universal approval router, adopted widely across DeFi. From the user’s seat it looks similar to an approval, but the blast radius is different.

  • What it authorizes: spending routed through the Permit2 contract. If you have previously approved Permit2 broadly — as many DEX users have — a malicious site can use Permit2 flows to reach tokens you never associated with this interaction.
  • How drainers use it: kits request Permit2 approvals on claim pages because one prompt can touch a wide set of holdings, and users rarely reason about which tokens a router can access. We break down the exploit mechanics in Permit2 exploits explained, and the Permit2 glossary entry covers the design.
  • How to read it: any Permit2 prompt on a site you came to for an airdrop is a near-certain drain attempt. Legitimate claims almost never need a DEX router.

Signature type 3: the permit signature (EIP-2612)

Permits accomplish what approvals do — granting an allowance — with an off-chain signature instead of an on-chain transaction.

  • What it authorizes: the same spending rights as an approval, but assembled by the attacker on the backend. No gas, no pending transaction, nothing in your activity feed.
  • Why drainers love it: the signature feels weightless. There is no gas estimate, no network prompt — just a “sign to verify” click. The attacker submits the permit plus the transfer themselves, sometimes bundled into one atomic operation.
  • How to read it: if the request is a typed-data permit, read the spender and value fields — that is the attacker’s contract and your allowance. Our permit sign phishing glossary entry covers the anatomy.

Signature type 4: raw eth_sign

The most dangerous and — thanks to wallet warnings — increasingly rare.

  • What it authorizes: an arbitrary message signature. On some wallet and chain combinations, that arbitrary blob can be interpreted as a transaction the attacker broadcasts without you.
  • How it appears: a claim page triggers a “sign message” prompt showing an unreadable hex blob. The site calls it verification, KYC, or a security check.
  • Why it still matters: when it works, it is total — the signature can underwrite a transaction moving everything you hold on that account. The full breakdown is in eth_sign phishing explained.

A newer fifth category — EIP-7702 delegation signatures — deserves its own treatment because it changes what “one signature” can do to an EOA. Read EIP-7702 airdrop phishing before claiming anything on a chain where Pectra features are live.

The 20-second prompt audit

Before confirming any claim-related signature, run this sequence:

  1. Function name. approve, permit, permit2, or unknown? “Unknown” on a claim page means decline.
  2. Spender. Copy the spender address into a block explorer. New contract, no verified source, deployed yesterday? That is a wallet drainer profile.
  3. Allowance. Any unlimited figure is a no for an unfamiliar site.
  4. Decodability. If your wallet shows raw hex instead of decoded fields, you are blind signing — decline by default.
  5. Wallet. Whatever the answer, sign with a wallet whose total balance you can afford to lose; the burner wallet claim workflow makes this automatic.

The deeper version of this audit — including explorer checks on the claim contract itself — is in airdrop scam checking in 5 steps, and all checks are consolidated in the airdrop safety checklist. This article is part of our Airdrop Safety series.

Frequently Asked Questions

Can an airdrop claim drain my wallet without me sending a transaction?

Yes. If the claim asks you to sign a token approval, a Permit2 approval, or a permit signature, you are granting spending rights rather than sending funds. The attacker's contract later moves your tokens under that authorization, and the transfer never appears as a confirmation in your wallet. This is why victims often describe the theft as silent and instantaneous.

What is the difference between an approval and a permit signature?

A standard approval is an on-chain transaction you pay gas for, granting a spender an allowance over your tokens. A permit signature (EIP-2612) achieves the same spending authorization with an off-chain signature — no gas, no transaction, instant. Drainer pages love permits because signing feels weightless. Both authorize spending; only the mechanics differ.

Why is Permit2 more dangerous than a normal approval?

Permit2 is a universal approval router used by major DEXs. Approving Permit2 broadly can let a malicious contract pull any token the router can reach, and its allowances do not always map to the per-token limits users expect. In claim contexts, drainer kits ask for Permit2 approvals precisely because the blast radius is your whole token balance. Treat any Permit2 prompt on an unfamiliar site as a drainer signal.

What does eth_sign phishing do?

eth_sign asks your wallet to sign an arbitrary blob. Depending on how the wallet and chain handle it, that blob can be a full transaction the attacker broadcasts later — including transfers of everything you hold. Most modern wallets warn about or disable raw eth_sign for this reason. If a claim site ever triggers a raw sign request with unreadable data, close the tab; we cover this attack in depth in eth sign phishing explained.

How do I read a signature request safely?

Three fields decide everything: the function being called (approve, permit, or something you do not recognize), the spender address (who gains rights — paste it into a block explorer), and the allowance amount (unlimited is a red flag). If your wallet cannot decode the request and shows raw data, that is blind signing — decline it. Simulation features in modern wallets will preview what a transaction does before you confirm.