Gas Fees and Transaction Security: Avoiding Malicious Contract Asset Drain

Introduction

In the blockchain world, every on-chain operation depends on Gas fees. They are the “fuel” that powers network activity but also become targets for malicious actors. From unlimited approvals silently transferring assets to Gas hijacking causing users to pay far more than expected, these traps are becoming increasingly covert.

Unlike traditional phishing attacks, these scams often disguise themselves as legitimate actions such as “approvals,” “minting NFTs,” or “participating in DeFi mining.” They exploit users’ unfamiliarity with contract mechanisms, gradually consuming or stealing assets without detection. To help everyone recognize these risks, ZeroTech Security Team combines industry security practices to focus on Gas fees and transaction safety, dissect common traps, teach practical prevention techniques, and clarify emergency response plans after asset loss.

Prat 01 - Common Gas Fee and Transaction Security Traps

Gas fees serve as the “pass” for on-chain transactions, and the security of related operations directly impacts user asset safety. Malicious actors exploit users’ lack of understanding of Gas mechanisms and approval processes by designing various covert traps, often disguised as normal on-chain interactions, making them difficult to detect. The main traps are categorized into three types:

1. Unlimited Approvals

Unlimited approval occurs when users grant a smart contract “unlimited” permission to use a certain token in their wallet. This is one of the most common and dangerous asset loss traps.

◆ Operation Logic: When you click “Approve” in a DApp, if you don’t carefully check the approval amount, you may have signed an “unlimited approval” agreement. This means the contract can theoretically transfer all your tokens of that type at any time without further confirmation.

◆ Typical Scenario: Minting niche NFTs, participating in unverified DeFi liquidity mining, or trading on unknown DEXs often involve malicious contracts defaulting to “unlimited approval,” prompting quick confirmation. Later, assets are transferred in bulk from your wallet without your awareness.

2. Gas Fee Hijacking

Gas fee hijacking refers to attackers manipulating malicious contracts or transaction data to force users to pay excessively high Gas fees or directly steal the Gas fees paid. Essentially, they control Gas parameters to gain illegal profits.

◆ Operation Logic:

Front-end Tampering: Attackers control the front-end of a DApp, automatically setting Gas prices or limits to extremely high levels during transaction initiation, far exceeding normal network congestion costs.

Malicious Contract Consumption: Malicious contracts embed “infinite loops” that continuously consume Gas during execution until the user’s Gas limit is exhausted, causing transaction failure but deducting Gas fees on the blockchain.

◆ Typical Scenario: Users participate in popular NFT whitelist mints via unofficial links. After clicking confirm, their wallets are instantly charged dozens of times the normal Gas fee, yet the NFT is not received.

3. Fake Approvals / Fake Transactions

Attackers forge approval requests or transaction pop-ups to trick users into signing malicious data, directly stealing assets or taking control of wallets. These often occur alongside Gas fee traps.

◆ Operation Logic:

Phishing誘導：用户点击钓鱼邮件、Discord私信或社交媒体广告中的“官方链接”，进入高度仿冒的假网站。

恶意请求伪造：假网站弹出的“授权”窗口，表面显示“授权代币用于交易”，实际上交易数据已被篡改，指令将用户资产直接转移到攻击者钱包。

◆ Typical Scenario: Users receive private messages claiming “Wallet security risk, urgent authorization needed,” click the link, complete authorization, pay high Gas fees, and their main tokens are instantly drained.

Prat 02 - Wallet Security Settings and Prevention Measures

To counter these Gas fee and transaction security traps, the key is “pre-emptive prevention.” Users don’t need deep blockchain technical knowledge—just focus on approval management, Gas fee settings, and transaction verification, cultivating good habits to effectively avoid risks. Specific measures include:

1. Strictly Control Approval Limits, Follow “Minimal Approval” Principle

Approval operations are the main vulnerability for asset loss. Controlling approval limits cuts risks at the source—“do not approve more than necessary, revoke unused approvals.”

◆ Reject Unlimited Approvals: When approving in any DApp, avoid default options; choose “Custom limit,” only authorize the minimum tokens needed for the current operation (e.g., mint NFT with 0.01 ETH approval, or approve only the transaction amount).

◆ Approve on Demand, Revoke Immediately After Use: For temporary interactions, revoke approvals immediately after completing the operation; for long-term compliant DApps, regularly review approval limits to prevent vulnerabilities from contract bugs.

2. Fine-tune Gas Fee Settings to Prevent Malicious Hijacking

Gas fee parameter settings are crucial for preventing Gas hijacking. Users should actively control Gas fee permissions, avoiding manipulation by malicious front-ends or contracts, reducing unnecessary costs and risks.

◆ Enable Advanced Gas Control: Use features like “Advanced Gas Management” in popular wallets (MetaMask, TokenPocket), manually set maximum Gas price and limit, preventing malicious front-end tampering.

◆ Refer to On-Chain Data: Before initiating transactions, check current average Gas prices via Etherscan, Arbiscan, etc., and reject requests with fees significantly above market levels.

◆ Avoid Peak Congestion Periods: During high-demand events like NFT mints or major policy releases, network Gas fees spike. Pause non-urgent operations or use Layer 2 solutions to reduce costs and risks.

3. Strengthen Transaction Security, Avoid Basic Traps

Besides approval and Gas settings, verifying transaction details and interaction scenarios is vital. Always “double-check and be cautious of suspicious activity.”

◆ Verify Core Transaction Info: When confirming in wallet pop-ups, check three points—whether the contract address matches official sources, transaction amount correctness, and Gas fee reasonableness; missing any is risky.

◆ Verify DApp Authenticity: Only access DApps via official websites or verified social media accounts. Check SSL certificates and contract addresses; avoid clicking unknown links.

◆ Isolate Risk Assets: Use a “dual-wallet” strategy—keep small amounts of assets in hot wallets for daily interactions, store large assets in hardware or cold wallets to isolate on-chain risks.

Prat 03 - Asset Loss Response and Recommended Tools

Despite precautions, malicious attacks can still occur due to negligence. Quick and accurate response minimizes losses. ZeroTech Security Team combines practical experience to provide “emergency steps” and “must-have security tools,” helping users take control during crises.

1. Emergency Response in Three Steps (Golden 10 Minutes)

Approval operations are the main entry point for asset loss. Controlling approval limits cuts risks at the source—“no excessive approvals, revoke immediately if suspicious.”

◆ Freeze Wallet and Revoke Approvals Immediately: Upon detecting abnormal transfers or high Gas fees, immediately use wallet “Pause” features to freeze operations; simultaneously, use approval management tools to revoke all suspicious contract approvals, cutting off attacker asset transfer channels.

◆ Collect Evidence and Report: Take screenshots of transaction hashes (TxID), malicious contract addresses, approval records, DApp links; submit transaction hashes to block explorers, mark as “suspicious attack”; report to wallet providers and DApp platforms for assistance.

◆ Seek Professional Security Help: For large asset losses, contact specialized blockchain security firms (e.g., ZeroTech), provide complete evidence chain. Security teams can trace attacker fund flows via on-chain analysis, assist in law enforcement coordination, and attempt to freeze involved addresses.

2. Essential Blockchain Security Tools

To help users maintain daily security and quickly respond to risks, four practical tools are recommended, covering approval management, transaction verification, and risk alerts—industry-recognized security tools:

3. Common Mistakes to Avoid (Pitfall Guide)

To help users in daily security practices and risk response, four practical tools are recommended, covering approval management, transaction verification, and risk alerts—industry-recognized security tools:

◆ Mistake 1: Paying “Unfreeze Fees” to Recover Assets— Attackers may ask for tokens under the pretext of “helping freeze involved addresses,” which is a scam. Do not trust.

◆ Mistake 2: Deleting Wallets to Solve Issues— Deleting a wallet does not revoke contract approvals; assets can still be transferred. The correct approach is to revoke permissions first, then reset the wallet.

◆ Mistake 3: Ignoring On-Chain Traceability— After large losses, it’s impossible to track fund flows alone; professional agencies and law enforcement are needed. Never give up on rights protection.

Conclusion

Gas fees and transaction security are the “first line of defense” in the blockchain world. Traps like unlimited approvals and Gas hijacking exploit users’ complacency and lack of technical understanding. When interacting with various DApps, remember the three principles: “Minimize approvals, slow down transactions, act quickly after loss” to effectively avoid most risks.