BigONE Crypto Exchange Hack: How $27 Million Was Stolen Without Private Keys

The cryptocurrency industry faced another major security breach in July 2025 when BigONE exchange suffered a sophisticated cyber attack resulting in $27 million in stolen funds. What makes this incident particularly concerning is that hackers managed to drain hot wallets without ever accessing private keys, highlighting new vulnerabilities in centralized exchange infrastructure.

What Happened in the BigONE Exchange Attack

On July 16, 2025, the Seychelles-based cryptocurrency exchange BigONE confirmed a major security incident. Cybercriminals executed a supply chain attack that compromised the exchange's production network, allowing them to drain $27 million from hot wallets through internal system manipulation.

The attack was unique because no private keys were compromised during the exploit. Instead, hackers manipulated internal systems to grant unauthorized fund withdrawals across various digital assets. BigONE officials confirmed that the threat was contained and customer private keys remained secure throughout the incident.

Stolen Assets Breakdown

According to on-chain data analysis, the attackers successfully extracted:

• 121 Bitcoin (BTC)

• 350 Ethereum (ETH)

• 9.69 billion Shiba Inu (SHIB)

• 538,000 Dogecoin (DOGE)

• Various amounts of Tether USDT and other digital assets

The exchange quickly restored its services including deposits and trading while partnering with blockchain security firm SlowMist to trace the stolen funds and investigate the attack vectors used.

How the Supply Chain Attack Was Executed

Unlike traditional crypto exchange hacks that target private keys or smart contract vulnerabilities, the BigONE attack exploited weaknesses in the exchange's back-end infrastructure. This sophisticated approach represents an evolution in cybercriminal tactics targeting centralized exchanges.

Initial Compromise Through Social Engineering

According to HackenProof, a cybersecurity bug bounty platform, the attack began with social engineering tactics. Criminals specifically targeted a key BigONE developer to compromise their device, gaining unauthorized access and elevated permissions within the exchange's systems.

Malicious Code Deployment

With unauthorized access secured, hackers deployed malicious code that temporarily altered the logic of accounting and risk management services within the exchange. This manipulation allowed them to bypass internal security controls and authorize fraudulent withdrawals from hot wallets.

Precision Fund Extraction

Once internal logic was compromised, the fund extraction occurred with remarkable precision. Attackers moved assets rapidly, with millions vanishing almost instantly. Cleanup transactions totaling 102,000 USDC and 79,000 USDT revealed extensive pre-planning and deep understanding of BigONE's internal systems.

Blockchain Investigation and Fund Tracing

Following the hack, BigONE partnered with blockchain security firm SlowMist to investigate the incident and trace stolen funds. SlowMist confirmed the attack methodology and published the addresses used in the heist across Ethereum and BNB Chain networks.

Money Laundering Techniques

Analysis from blockchain observatory company Lookonchain revealed that attackers began laundering stolen assets through multiple blockchain networks including Tron, Solana, Ethereum, and Bitcoin. This multi-chain approach makes fund recovery significantly more challenging.

The exchange established a bounty program offering up to $8 million in rewards for useful intelligence leading to attacker identification and successful fund recovery. Despite these efforts, determining the final destination of stolen funds remains challenging for investigators.

Advanced Laundering Methods

Criminals employed increasingly sophisticated money laundering techniques, including leveraged trading on decentralized exchanges to open large positions and hedge them with clean capital. These evolving tactics demonstrate the growing sophistication of crypto criminals.

Supply Chain Vulnerabilities in Crypto Exchanges

The BigONE incident highlights critical differences between cryptographic security focused on protecting private keys and infrastructure security that maintains system integrity. Many centralized exchanges rely heavily on continuous integration systems for rapid software updates, creating potential attack vectors.

Critical Infrastructure Risks

Single points of failure, such as compromised developer accounts, can lead to malicious code injection that bypasses traditional security safeguards. Systems can be reprogrammed to allow fund extraction while remaining undetected by monitoring systems designed to identify external threats rather than internal compromises.

This attack methodology represents a significant evolution from simple phishing scams, now incorporating social engineering, malicious contract deployment, UI spoofing, and deepfake deception as standard practices among sophisticated cybercriminals.

2025 Crypto Exchange Security Landscape

The BigONE hack joins a concerning list of major crypto security incidents in 2025, including CoinDCX losing $44 million, GMX suffering a $40 million exploit, and Arcadia Finance losing $3.5 million. These incidents demonstrate that crypto attacks are becoming more frequent and sophisticated.

Industry Impact and Insurance Response

The crypto insurance market has grown significantly from $1.3 billion in 2023 to $4.2 billion in 2025, with exchange premiums rising 35% year-over-year in Q1 2025. This growth reflects the escalating security challenges facing the cryptocurrency industry.

Total cryptocurrency thefts already exceeded $2.5 billion in the first half of 2025, surpassing total annual losses recorded in 2024. This trend suggests that blockchain security firms are experiencing unprecedented demand for their services.

Protective Measures and User Compensation

BigONE implemented several protective measures following the attack. The exchange's insurance reserve fund covered all user losses, ensuring customers were fully compensated for the stolen assets. System vulnerabilities were identified and patched to prevent similar attacks.

The exchange uses tiered security systems including fund segregation across different storage areas and maintains substantial insurance reserves to reimburse customers when losses occur. These protective measures helped minimize the impact on users despite the significant security breach.

Key Takeaways for Crypto Users

The BigONE supply chain attack demonstrates that even sophisticated exchanges with strong cryptographic security can be vulnerable to infrastructure-based attacks. Users should consider diversifying their holdings across multiple exchanges and utilizing hardware wallets for long-term storage.

This incident reinforces the importance of understanding that exchange security involves multiple layers beyond private key protection, including infrastructure security, employee access controls, and supply chain integrity. As attacks become more sophisticated, the crypto industry must adapt its security practices accordingly.

The growing frequency and sophistication of crypto exchange attacks in 2025 highlight the ongoing challenges facing centralized platforms and the critical importance of robust security measures across all aspects of exchange operations.

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