In DeFi, you skip the bank and interact with software. That sounds clean until you remember one detail: software breaks, and people lie. When you connect a wallet to a dApp, you let code touch your funds. If the code is weak or the app is malicious, you can lose everything.
Most users start in a crypto exchange and that is fine.
Exchanges like Bitunix handle custody and some security controls for you, which can reduce certain on-chain risks. But the moment you move on-chain to invest in DeFi, you switch roles. You become the risk team, the compliance team, and the person who clicks confirm.
This guide is not about learning to code. It's about learning to be a defensive user. We will cover the biggest risks you face when interacting with smart contracts and provide a practical checklist to help you protect your assets.
What is Smart Contract Risk?
Smart contract risk is the chance that the code you interact with does something you did not expect, or that someone exploits it to take funds. Smart contracts are often immutable after deployment, so a bug can live on-chain for a long time. Some projects use upgrade mechanisms, but upgrades introduce a different risk, including that admin keys and governance decisions can change behavior after you deposit.
Think of it like handing your car keys to a valet. You expect parking. But you just handed over the ability to move the car. On-chain permissions work the same way. When you approve a contract, you give it the ability to move tokens that belong to you, and that permission can stick around long after you forget it.
A DeFi wallet is powerful and risky because it gives you direct access to dApps, and those dApps can access your assets once you approve them. The losses in 2025 show how often attackers target users. CertiK tracked $2.47B lost in H1 2025, with wallet compromise alone at about $1.71B (34 incidents) and phishing at about $410.7M (132 incidents). Chainalysis estimated $3.4B stolen in 2025, and TRM Labs reported $2.87B stolen across nearly 150 hacks, driven heavily by a single mega-breach.
The Most Common Smart Contract Risks
Most on-chain disasters fall into a few repeating patterns. You will see different branding and different chains, but the mechanics stay familiar. Below are three risks that matter for almost every DeFi user and NFT collector.
Re-entrancy Attacks (The Classic Hack)
A re-entrancy bug happens when a contract sends funds before it updates its internal balance. An attacker calls the withdraw function, receives funds, and then re-enters the same function again before the contract finishes updating state.
The DAO hack in June 2016 is the classic re-entrancy cautionary tale. An attacker drained about 3.6 million ETH, roughly a third of the 11.5 million ETH raised, by repeatedly triggering a withdrawal path before the contract updated balances, and the funds sat in a child contract with a built-in waiting period. The fallout led to Ethereum’s July 20, 2016, hard fork at block 1,920,000, which moved roughly 12 million ETH into a recovery contract and ultimately split the network into Ethereum and Ethereum Classic.
Rug Pulls (Malicious Code)
Sometimes nothing is buggy. It is designed to steal. A rug pull scam usually relies on privileged functions that let deployers drain a pool, mint unlimited tokens, block sells, or change fees after liquidity arrives. Users deposit because the UI looks clean and the APY looks tempting, then the exit door locks.
This risk is higher in new tokens, new farms, and copy-paste contracts. It also shows up in NFT mints, where the mint page asks you to sign something that gives broad rights. You reduce this risk by checking who controls admin keys, whether the code is verified, whether the team has a track record, and whether reputable communities have stress-tested the project.
Unlimited Token Approvals (The Silent Threat)
When you swap on a DEX or use a lending protocol, you usually approve a contract to spend your tokens. That is how the contract can move your USDC, ETH, or NFTs on your behalf. Revoke.cash explains token approvals as permissions that let a smart contract spend your tokens for you, and it also explains that NFT approvals can be limited to a single token or unlimited for a whole collection.
The convenience trap is unlimited approvals. Many apps ask for unlimited approval so you can trade again without repeating the approval transaction. If that contract gets exploited later, a thief can use the existing approval to drain that token from your wallet, even if you are not on the site.
Revoke.cash even tracks approval-related exploits where attackers abuse approvals to steal funds outside the exploited contract’s own balance. Wallet drainers also lean on these permissions, and Trust Wallet warned in 2025 that lingering approvals can expose you to unauthorized access.
Your Security Checklist: How to Protect Yourself
You cannot remove all risk in DeFi. You can remove the easy wins attackers love. The checklist below focuses on actions you can repeat, so you do not rely on memory when you are tired, excited, or rushing. This is the practical side of DeFi security and how to avoid crypto scams without turning into a full-time investigator.
DYOR (Do Your Own Research)
Start with the basics that scammers cannot fake easily. Check whether the team is public and whether they have shipped anything before. Anonymous teams can be legitimate, but you should treat them as higher risk by default.
Then look at the community. Real projects have disagreement, bug reports, and support threads. If you only see good feedback and referral codes, step back. Also check whether the docs match the product. Thin docs and thick marketing is a common red flag.
Check for Audits
A smart contract audit is a third-party review where a security firm inspects code, tests common exploit paths, and documents findings. Audits help, but they do not guarantee safety. Attackers also target front-ends, admin keys, and users.
The Trail of Bits Blog put the real problem bluntly in a 2025 security post:
"design protocols that can safely tolerate private key compromise"
As a user, read audits like you read a home inspection report. Look for scope, commit hash or version, severity of findings, and whether the team fixed issues with a follow-up review. If the site says audited but provides no report, treat that as not audited.
Use a Burner Wallet
Separate your funds by purpose. Keep a main wallet for long-term holdings and a second wallet for new dApps, mints, and experiments.
The numbers back this up. CertiK’s H1 2025 report said wallet compromise was the most costly attack vector, with about $1.71B stolen across 34 incidents, and phishing was next with about $410.7M stolen across 132 incidents.
Even large players can fall to signing tricks. In its technical analysis of the Bybit incident, CertiK described a phishing attack that deceived wallet signers into signing malicious transaction data, leading to a contract upgrade that enabled the drain.
Revoke Your Approvals
Approvals are not a one-time decision. They are ongoing permissions, and you should review them like you review app permissions on your phone.
Revoke.cash provides an approval checker and a simple process: connect or enter your address, inspect approvals, and revoke the ones you do not use. When you revoke, your wallet signs a transaction, and you pay a small gas fee.
A practical routine works well for most people:
Revoke approvals after you stop using a dApp.
Revoke the unlimited approvals you granted months ago.
Review NFT approvals after any minting spree, since marketplaces often use broad approvals.
If It Looks Too Good to Be True, It Is
Extreme APYs often exist to pull in deposits fast. Sometimes the project collapses because the token emissions are unsustainable. Other times, it is outright theft.
Tie this back to the broader threat landscape. Chainalysis described 2025 as a high-loss year with more than $3.4B stolen, and TRM Labs said 2025 losses were highly concentrated with a single mega-incident driving a large share of theft. When attackers earn billions, copycats appear.
Conclusion: Be Paranoid, Be Protected
You cannot outsource safety on-chain. You can reduce your risk a lot with a few habits, such as researching before you deposit, preferring audited code with clear reports, using a burner wallet, and revoking approvals regularly.
Smart contract security works best when you treat it as a routine, not a one-time setup. If you trade on exchanges like Bitunix, you operate in a more centralized environment with different protections. When you go on-chain, use the checklist above so your curiosity does not turn into a donation.
At Bitunix, we operate in a secure, centralized environment to protect you from the inherent risks of the decentralized world. For your on-chain adventures, use the strategies in this guide to stay safe. For your trading needs, download the official Bitunix app, create an account, and trust the proven security of the Bitunix platform.
