Cryptographic systems underpin decentralized finance (DeFi) and blockchain ecosystems, offering users unparalleled control over digital assets. However, the sophistication of these systems also opens up a variety of attack vectors, from smart contracts to multisig wallets, and even hardware wallets. Developers, often focused on functionality, may overlook critical vulnerabilities, creating opportunities for sophisticated attacks like those seen in the Radiant Capital $50M hack. This article will explore the vulnerabilities within crypto systems and provide detailed insights into how they occur, drawing on the latest attack trends and often-overlooked developer mistakes.

1. Smart Contract Vulnerabilities
How They Occur:
Smart contracts are self-executing contracts with the terms of the agreement directly written into code. Their functionality is often complex, and errors or #vulnerabilities in the code can lead to catastrophic results. Hackers can exploit issues such as:
- Reentrancy Attacks: When a smart contract calls an external contract, attackers can use #reentrancy to exploit the sequence of code execution, draining funds.
- Example: In the 2016 DAO attack, reentrancy was used to repeatedly withdraw funds before the contract’s balance was updated, resulting in $60M of stolen $ETH .

- Unchecked Return Values: Developers often overlook checking the return values of low-level calls. This can lead to a contract assuming a call has succeeded when it has not, leaving the contract vulnerable to exploitation.
- Integer Overflow/Underflow: If a contract uses arithmetic operations without proper checks, overflow and underflow issues can occur. Attackers can #exploit these to create infinite tokens or drain funds.

- Exploiting Token Approvals: Many DeFi protocols require users to approve token transfers. Attackers can exploit ongoing approvals or smart contracts that fail to properly manage token allowances.
Mitigation Measures:
- Use Libraries: Utilize audited libraries like OpenZeppelin to avoid common pitfalls in solidity programming such as integer overflow.
- Reentrancy Guards: Include reentrancy guards to prevent recursive calls that could drain funds.
- Audit Smart Contracts: Regularly audit contracts to detect vulnerabilities before deployment.
- Limit Permissions: Encourage users to regularly review and revoke token approvals using tools like Etherscan’s token approval checker.

2. Multisig Wallet Vulnerabilities
How They Occur:
Multisig wallets (e.g., Gnosis Safe) require multiple private keys to authorize transactions, creating a barrier against single-point failures. However, if one or more signers are compromised, the system’s security can break down. Here’s how #Multisig wallets can be attacked:
- Endpoint Compromise: Attackers can install malware, such as a Trojan, on team members' computers. This malware can intercept and modify signing requests before they are sent to the multisig wallet. In the Radiant Capital hack, a Trojan altered transaction data, tricking the hardware wallet into signing a malicious transfer of ownership without detection.

- Hardware Wallet Interception: While hardware wallets are designed to securely sign transactions, they can still be manipulated if the device used to interact with the hardware wallet is compromised. If malware intercepts the transaction data before it reaches the hardware wallet, the user unknowingly approves a malicious transaction.
- Atomic Execution Exploits: Attackers bundle several malicious actions (e.g., ownership transfers, contract upgrades) into one atomic transaction, making it nearly impossible to stop or detect the malicious activity before the funds are stolen.
Mitigation Measures:
- Endpoint Security: Implement anti-malware solutions on devices used for signing transactions. Keep these devices isolated from internet access where possible to reduce the risk of malware infections.

- Cross-verification of Transactions: Ensure that all multisig signers review transaction data on different devices to detect any manipulation. If the same transaction appears differently on separate devices, it should trigger an immediate investigation.
- Timelocks and Governance: Introduce timelocks to delay critical operations such as ownership transfers or large fund movements. Use governance processes to require community or multi-layer multisig approval for contract upgrades or ownership changes.

3. Hardware Wallet Vulnerabilities
How They Occur:
Hardware wallets provide offline storage of private keys, adding a layer of security against #hacks . However, they can still be exploited through indirect means:
- Man-in-the-Middle Attacks: If a computer interacting with a hardware wallet is compromised, attackers can intercept and alter transaction requests before they are displayed on the hardware wallet screen. The user might sign a transaction believing it is legitimate, when in reality they are approving a malicious one.
- Physical Attacks: Supply chain attacks can compromise hardware wallets at the manufacturing level, where malware is introduced during the production process. If the hardware wallet is tampered with before it reaches the user, attackers can potentially access the private keys.
- Malware-Based Attacks: Like in the Radiant Capital hack, Trojans can replace legitimate transactions with malicious ones before they are sent to the hardware wallet, leading to unauthorized actions, such as contract upgrades or ownership transfers.
Mitigation Measures:
- Use Air-gapped Devices: Sign transactions using air-gapped devices that are not connected to the internet to reduce exposure to malware.

- Cross-check Transactions: Ensure users always check the transaction details on their hardware wallet’s screen before confirming, comparing them with the intended action.

- Regular Firmware Updates: Keep hardware wallets updated with the latest firmware to patch any potential vulnerabilities.

- Device Authentication: Use hardware wallets from reputable manufacturers that include device authentication mechanisms to prevent tampering during the supply chain process.

4. Multisig Best Practices and Signature Verification
Even though multisig wallets add layers of security, they are not foolproof. Weaknesses often arise from how multisig transactions are verified and executed, particularly in setups involving hardware wallets.
How Vulnerabilities Occur:
- Compromised Signers: If one or more signers in a multisig wallet are compromised, attackers can manipulate transaction requests, as seen in the Radiant Capital hack. The infection of team members' computers allowed for manipulation of multisig transactions before the hardware wallet even signed them.

- Weak Cross-Verification: Multisig signers may assume that because they are in a secure setup, they do not need to verify transactions across multiple devices. This assumption can be exploited by attackers who alter transaction requests at the endpoint.
Mitigation Measures:
- Distributed Signing: Multisig signers should verify transactions across multiple devices and display methods to detect potential discrepancies in the data.

- Anomaly Detection: Use anomaly detection systems to flag unusual transactions for review. Any inconsistencies between what is shown to different multisig signers should trigger a halt in the transaction.

5. Mitigation Lessons from Radiant Capital's Attack
The Radiant Capital hack is a reminder that even the most sophisticated systems are vulnerable to multi-layered attacks that blend malware, multisig exploitation, and hardware wallet manipulation. The attack showed that combining multiple vulnerabilities (Trojan malware, hardware wallet interception, and atomic execution) can create an exploit that bypasses many traditional defenses.
Key lessons:
- Always Assume Endpoints Can Be Compromised: Even with a secure hardware wallet, attackers can intercept and modify transactions at the computer level. Therefore, endpoint security must be a top priority.

- Atomic Execution Monitoring: Implement real-time monitoring of atomic transactions that can flag malicious activity before they are executed on-chain.

- Governance and Timelock Mechanisms: Timelocks should be mandatory for sensitive operations, and governance processes should be in place to delay or prevent suspicious actions.
By adopting a multi-layered approach to security, including smart contract audits, endpoint protections, and cross-verification of transactions, developers and users can better safeguard their assets from the increasingly sophisticated landscape of crypto exploits.