Approval / Allowance Phishing

ERC-20 and other token standards include an approve function that lets a smart contract spend tokens on the holder's behalf up to a specified limit. DeFi protocols use this legitimately (for example, allowing a DEX to pull tokens when you trade). Approval phishing exploits this by presenting a transaction that looks benign but secretly grants an attacker-controlled contract an unlimited spending allowance.

Victims typically encounter this through fake airdrop claims, counterfeit DeFi frontends, or malicious pop-ups. After granting the approval, the attacker can drain the wallet at any time, sometimes waiting days or weeks to avoid detection.

Regularly reviewing and revoking unnecessary approvals using tools like Revoke.cash or Etherscan's token approval checker is one of the most important ongoing hygiene steps for any active DeFi or NFT user.