Approval Drainer Attacks in the Hyperliquid Ecosystem

May 11, 2026

Approval drainers are one of the lowest-effort and fastest-growing ways attackers steal crypto assets. They do not need to crack your private key or execute a sophisticated on-chain exploit. They only need you to “voluntarily” sign a transaction or message you do not fully understand.

With HyperEVM bringing richer on-chain activity to the Hyperliquid docs ecosystem, Hyperliquid users now face more of the same approval-drainer risks that have long existed across EVM chains. This article explains how these attacks work, why HyperEVM changes the risk profile, and what you can do to reduce your exposure.

Chainalysis research has shown that drainer kits have become a mature underground industry. Attackers can deploy customized drainer contracts at low cost and distribute them through phishing sites, fake airdrops, and malicious DApps at scale.

How approval drainers work

To understand drainer attacks, you first need to understand the ERC-20 approve mechanism.

The ERC-20 standard defines an approve function that lets a token holder authorize another address, usually a smart contract, to move tokens on their behalf up to a specified amount. This is a core building block of DeFi. For example, when you swap tokens on a DEX, you usually approve the exchange contract to access the token you want to trade.

Approval drainers abuse this same mechanism:

The attacker deploys a malicious contract designed to transfer assets after receiving approval.
The attacker lures users into interacting with it through a fake website, fake airdrop, or malicious DApp.
The user signs what looks like a routine approval transaction, but the approval gives the malicious contract permission to move one or more tokens.
The malicious contract quickly transfers the approved tokens out of the user’s wallet, often in the same block or shortly after.

The whole process can take seconds. Once an approval is confirmed on-chain, the attacker can use it at any time until the approval is revoked or the approved balance is gone.

Why HyperEVM introduces new approval risk

HyperEVM is Hyperliquid’s EVM-compatible execution environment. It allows standard Ethereum-style smart contracts to run in the Hyperliquid ecosystem. That opens the door to a much broader DeFi surface area, but it also imports the same approval and signature risks that EVM users already know from Ethereum and other EVM chains.

On HyperEVM, drainer variants may include:

Phishing pages that pretend to be native HyperEVM DApps and ask users to approve malicious contracts.
Drainers that abuse EIP-2612 Permit signatures, where users sign an off-chain message instead of sending an on-chain transaction.
Fake front ends that copy legitimate HyperEVM protocol interfaces but insert extra approval requests during normal user flows.

EIP-712 structured signing improves readability compared with raw messages, but many users still do not understand what they are signing. That gap is exactly what Permit-based drainers exploit.

Permit signature drainers: the harder-to-spot variant

A traditional approval drainer triggers an on-chain transaction. In many wallets, the user will see something like “Token Approval,” which may be enough for an experienced user to stop and check the details.

Permit drainers are more subtle.

Instead of a transaction, the user sees a “Sign Message” request. The popup may show formatted data that looks like a login challenge, account verification, or routine DApp authorization. Many users assume that signing a message cannot move funds, then click confirm.

In reality, the message may be an EIP-2612 Permit authorization containing:

spender: the attacker’s malicious contract or address.
value: often the maximum U256 value, effectively an unlimited approval.
deadline: usually a far-future timestamp.

After the user signs, the attacker can broadcast the signed Permit and call transferFrom to move the user’s tokens. The user does not need to pay gas for the original signature, which makes the attack feel less suspicious.

How to reduce the risk of drainer attacks

1. Understand every transaction or signature request

Whenever your wallet shows a request, pause before confirming.

If it is a transaction, check:

Whether the to address is the contract you expected.
Whether the transaction data includes an approve call.
Whether the approval amount is reasonable.

If it is a message signature, check:

Whether it includes fields such as spender, value, deadline, or permit.
Whether the spender address is recognizable.
Whether the value looks like an unlimited approval.

If you do not understand what the request does, do not sign it.

2. Review and revoke unnecessary approvals

Use Revoke.cash to review active token approvals connected to your wallet. If you see approvals for contracts you do not recognize, or approvals for DApps you no longer use, revoke them.

A practical habit is to review approvals at least monthly, and especially after interacting with new DApps.

Revoking an approval costs gas, but it can prevent future transfers from an approval you forgot about.

3. Avoid unlimited approvals when possible

Many DApps default to “Max” approval because it is convenient. Convenience increases risk.

When a DApp asks for token approval, approve only the amount needed for the current action where possible. If you are tricked, your potential loss is limited to the approved amount instead of your full token balance.

4. Be extra cautious with new HyperEVM DApps

HyperEVM is a newer environment, and newer ecosystems often attract both builders and attackers. Unaudited protocols may have real bugs, and malicious projects may disguise themselves as early opportunities.

Before interacting with any HyperEVM DApp, check:

Whether you reached it through an official source, not a search ad or random social link.
Whether the project has credible documentation and community history.
Whether contracts have been audited or at least publicly reviewed.
Whether the wallet request matches the action you intended to perform.

Hyperliquid’s official documentation is a better starting point than links shared in Telegram, Discord, or search results.

5. Use a OneKey hardware wallet for physical confirmation

A hardware wallet adds an important layer of verification because the critical transaction or signature details are shown on the device itself, not only in the browser or wallet extension.

When handling approval requests, OneKey hardware wallets can display key details such as the spender and approval amount on the device screen. This helps protect against malicious websites that present friendly wording in the browser while hiding dangerous transaction data.

For Permit-style off-chain signatures, OneKey also helps users inspect structured signing content on the hardware device instead of blindly approving a message in the browser.

This does not make every interaction risk-free, but it improves the workflow: verify on the hardware screen, then confirm only when the details match your intent.

Drainer warning signs and response guide

Warning sign	Why it matters	What to do
A site asks for approval before showing any real function	It may be collecting token permissions first	Do not approve; verify the official source
The approval amount is “unlimited” or extremely large	A compromised or malicious contract can drain the full balance	Use a limited amount or reject the request
A “Sign Message” request includes `spender`, `value`, or `deadline`	It may be a Permit approval, not a harmless login	Reject unless you fully understand it
The DApp link came from Telegram, Discord, X replies, or search ads	These are common phishing distribution channels	Use bookmarked or official links only
A page claims urgent rewards, free airdrops, or time-limited access	Urgency is often used to suppress careful review	Slow down and verify independently
You already signed something suspicious	The attacker may still have active approval	Move unaffected assets if needed and revoke approvals immediately

FAQ

Q1: If I revoke an approval, can I recover tokens already stolen by a drainer?

No. Revoking an approval only prevents future transfers. It cannot reverse completed on-chain transactions. Once an on-chain transfer is confirmed, it is not reversible.

Q2: Is it safe to only view a suspicious website without connecting my wallet?

Simply visiting a site usually will not move assets, because a transfer requires a transaction or signature. However, malicious sites may try to exploit browser or extension vulnerabilities. If you must inspect a suspicious site, use a separate browser profile that does not contain wallets with funds.

Q3: What is the practical difference between EIP-2612 Permit and a normal approval?

A normal approve is an on-chain transaction and requires gas. An EIP-2612 Permit is an off-chain signature, so signing it does not require gas. But after you sign, the attacker can use that signature on-chain to authorize transferFrom and move tokens. The idea that “signing messages cannot cause losses” is wrong.

Q4: Can OneKey completely block drainer attacks?

No wallet can guarantee that. OneKey reduces the risk by adding physical confirmation and clearer transaction or signature review on the hardware device. But the final decision still depends on the user confirming only after understanding the request.

Q5: Which HyperEVM actions are most likely to involve drainer risk?

High-risk scenarios include claiming “free airdrops,” joining unknown liquidity mining campaigns, using DApps found through search results instead of official links, and clicking DApp links shared in Telegram or Discord groups. Always verify the source before connecting your wallet or signing anything.

Conclusion: understand every signature and verify with OneKey

Approval drainers are dangerous because they exploit user intent, not necessarily smart contract bugs. The attacker’s goal is to make a harmful approval look routine.

The strongest defense is a disciplined signing workflow: understand every transaction, inspect every message, avoid unnecessary unlimited approvals, and regularly revoke permissions you no longer need.

For Hyperliquid users, a practical setup is to use OneKey hardware wallet verification for on-chain interactions, keep approvals clean with tools like Revoke.cash, and trade Hyperliquid through OneKey Perps where it fits your workflow. OneKey Perps gives users a focused way to access Hyperliquid trading while keeping wallet security habits front and center.

Try OneKey and OneKey Perps as part of a safer Hyperliquid workflow. Visit onekey.so/download to learn more about OneKey hardware devices and the OneKey app.

Risk warning: This article is for informational purposes only and is not investment, financial, legal, or security advice. On-chain asset security is ultimately your responsibility. The practices described here can reduce risk, but they cannot guarantee protection against every attack. Always stay alert and treat every transaction or signature request with caution.