Chapter 15
Wallet drainers and token approvals
What you'll get from this chapter: How a fake “free mint” or “airdrop” page tricks you into giving away permission to empty your wallet, and how to cancel that permission.
In this chapter
- Words in this chapter
- Your steps
A site that offers free new tokens (a “”) or a free “” of coins may really be asking for permission to spend what is already in your wallet.
A is a web page that tricks you into signing a transaction. The page looks like a token sale, a free giveaway, or a limited release. Your wallet then asks you to approve it. A is permission for that site’s (the program that runs on the ) to move a token out of your wallet later, sometimes for an unlimited amount. You do not have to send coins yourself. The approval is enough.
Read the wallet prompt before you confirm it. If it says approve, permit, or set allowance, and you did not intend to trade on that site, reject it. If you already approved a site you do not trust, revoke the approval. Revoke means you cancel that permission. You can review and revoke approvals at revoke.cash, or in the token-approval checker on a such as Etherscan. Open those sites yourself. Do not use a link from the page that just asked you to sign.
One more crypto trick hides in plain sight: inside your own transaction history. The next chapter covers .
Words in this chapter
- . A website that tricks you into signing a transaction so it can take cryptocurrency out of your wallet.
- . Permission you grant a website or a contract to move a token from your wallet later. Revoke means you cancel that permission.
- . A program that runs on a and moves tokens by its own rules. A token approval gives a smart contract permission to move your tokens.