MetaMask Security Tips: How to Block Infinite Approval Scams

Are you a fan of web3 and decentralized applications (DApps)? Do you love using your ERC-20 tokens for various crypto activities like swapping, lending, and providing liquidity? If so, you need to be aware of a crucial feature that enables these interactions: token approval.


Token approval is like giving someone your credit card and telling them how much they can spend with it. It allows another DApp (called a spender) to access and move some of your tokens on your behalf. This way, you don’t have to send your tokens to the DApp directly, which could be risky or inconvenient.

But how does token approval work? And what are the risks involved? In this article, we will explain everything you need to know about token approval, how hackers can exploit it, and how you can protect yourself from MetaMask infinite approval attacks.

How Token Approval Works

Token approval is based on two functions that are part of the ERC-20 standard: approve () and transferFrom ().

The approve () function is what you use to grant permission to a spender to use some of your tokens. It requires two parameters: the address of the spender and the amount of tokens you want to let them use. For example, if Alice wants to let Bob use up to 100 tokens for her, she would call approve (Bob, 100).
The approve () function does not actually move any tokens. It just sets an allowance for the spender to use up to a certain amount of tokens from your account.

To actually move the tokens, the spender has to call another function, transferFrom (), which requires three parameters: the address of the token owner, the address of who gets the tokens, and the amount of tokens to be moved.

The transferFrom () function checks that the spender has enough allowance from the token owner, and that the token owner has enough tokens to move. If both conditions are true, it transfers the tokens from the owner’s account to the receiver’s account, reduces the spender’s allowance by the transferred amount and records the transfer.

For example, if Bob wants to use 50 tokens from Alice’s account to buy something from Charlie, he would call transferFrom (Alice, Charlie, 50). This would check tokens without you realizing it.

How Token Approval Can Be Exploited

Here are some of the most common methods:

• Phishing: Hackers can create fake websites or emails that look like legitimate DApps or platforms and ask you to approve an infinite amount of tokens for them. If you fall for their trap, they can use your tokens for their own benefit or sell them on the market.
• Front-running: Hackers can monitor the blockchain for pending transactions that involve token approvals and try to insert their own transactions before them. This way, they can change the address or the amount of tokens you are approving to their own address or an infinite amount.
• Smart contract bugs: Hackers can exploit vulnerabilities in smart contracts that you have already approved tokens for. For example, they can find a way to call the transferFrom () function multiple times with the same allowance, or bypass the checks that prevent them from using more tokens than you have approved.

How to Protect Yourself from Token Approval Attacks

The good news is that there are some simple steps you can take to protect yourself from token approval attacks and keep your tokens safe. Here are some of the best practices you should follow:

• Always check the address and the amount of tokens you are approving: Before you confirm any transaction that involves token approval, make sure you double-check the address of the spender and the amount of tokens you are allowing them to use. Don’t trust any links or QR codes that you receive from unknown sources. Use a block explorer like Etherscan to verify the address and the contract code of the spender.
• Don’t approve an infinite amount of tokens unless you really need to: Some DApps may ask you to approve an infinite amount of tokens for convenience or efficiency reasons. But this also exposes you to a lot of risk. Unless you really trust the DApp and have a good reason to do so, don’t approve an infinite amount of tokens. Instead, approve only the amount of tokens that you need for a specific transaction or period of time.
• Use tools and platforms that can help you review, revoke, or customize your token approvals: There are some tools and platforms that can help you manage your token approvals more easily and securely. For example, Revoke.cash is a platform that lets you see all your token approvals and revoke them with one click. Token Allowance Checker is a tool that lets you check the allowance of any ERC-20 token for any address. MetaMask also has a feature that lets you customize your token approval amount when interacting with DApps.
• Stay updated on the latest security news and alerts: The crypto space is constantly evolving and so are the threats and attacks. To stay safe, you should always keep yourself informed about the latest security news and alerts. Follow reputable sources like MetaMask, Etherscan, Rekt News, etc. on social media or subscribe to their newsletters. If you hear about any security breach or vulnerability affecting a DApp or a platform that you have approved tokens for, act quickly and revoke your approvals if possible.

Token approval is a powerful feature that enables many exciting possibilities in web3 and DApps. But it also comes with some risks and challenges that you need to be aware of and prepared for.

By following these tips, you can enjoy using your Crypto tokens without worrying about losing them to hackers. Stay safe and have fun!
So, this is it for this article. If you have any questions or doubts feel free to ask in the comments...

Also read, What is Slippage in Crypto and How to Minimize Its Impact.