How a single signature empties a wallet: approval and permit phishing

Modern wallet drainers rarely 'break in' to anything. They get you to authorize them. Two ordinary Ethereum mechanics do almost all of the work: the ERC-20 token approval, and the EIP-2612 'permit'.

A standard approval lets a contract spend your tokens up to a set limit, the same mechanism a real exchange uses. Grant an unlimited approval to the wrong contract and it can transfer that token out of your wallet whenever it chooses, with no further prompt.

The signature that looks like nothing

EIP-2612 makes this quieter. Per DarkNavy's technical breakdown, permit lets you grant a spending approval with an off-chain signature instead of an on-chain transaction: no gas, no confirmation window, just a 'Sign' dialog.

That framing is the trap. DarkNavy notes wallets have historically rendered these as generic 'sign this message' prompts, which users treat as harmless, far less consequential than sending a transaction. Yet the data being signed names a spender, an amount, and a deadline.

The attacker simply captures that signature and submits it to the token contract itself, calling permit and then transferFrom to move the funds. Because the approval was granted by signature, nothing appears in the victim's own transaction history; they pay no gas and see no transaction of their own, only, later, a drained balance.

Why it dominates the loss column

The scale is not hypothetical. Per Scam Sniffer's 2024 report, summarized by BleepingComputer, wallet drainers stole roughly $494 million in 2024, a 67% year-over-year jump, across more than 300,000 victim addresses, with the single largest theft at $55.4 million. About 56.7% of those losses relied on permit-style signature phishing.

**Before you sign, check:** - A 'Sign' request is not automatically safe; read exactly what it authorizes. - Look for fields like owner, spender, value and deadline, or a 'Permit' type: that is a spending grant, not a login. - Refuse a value set to an enormous number (unlimited) unless you truly intend it. - Favor wallets that decode signatures into plain language and simulate the result. - Review and revoke old token approvals periodically; keep savings in a separate, rarely-connected wallet.

The through-line is uncomfortable but clarifying: in Web3 the dangerous action is often not a transaction at all. It is a signature, and an entire criminal supply chain is built around getting you to produce one.

— Sources: [BleepingComputer](https://www.bleepingcomputer.com/news/security/cryptocurrency-wallet-drainers-stole-494-million-in-2024/) · [DarkNavy](https://www.darknavy.org/web3/exploits/usdc-permit-phishing-drain/)