Binance Hacked for $6.3 Billion: Cold Wallets Are No Longer Secure — Where Exactly Should Crypto Assets Be Stored?
Author: Jake Pahor (Co-founder of Crypto Super Hub, Senior On-chain Analyst)
Compiled by: TechFlow
TechFlow: Last Friday's devastating $6.3 billion heist at Binance brutally shattered the crypto industry's absolute illusion of security regarding centralized giants and multi-sig hot wallets. However, shifting toward full self-custody reveals a landscape equally fraught with traps this year—from Ledger supply chain implants and Coldcard firmware vulnerabilities to lost private keys and the complex compliance audits required for self-managed superannuation funds (SMSFs). Native on-chain physical control is no less treacherous.
Facing the darkest asset security crisis the industry has ever witnessed, renowned Australian on-chain researcher and Crypto Super Hub co-founder Jake Pahor penned this comprehensive guide on asset custody and risk management review. He not only objectively deconstructs the underlying technical causes of Binance's stolen 50 pre-signed withdrawal permissions and the evolution of North Korean hacker tactics, but also systematically outlines the pros, cons, and corresponding risk control measures across four major pathways from both individual and institutional perspectives: full self-custody, collaborative multi-signature setups (Unchained, Casa, Nunchuk, Bitkey), centralized exchanges, and Bitcoin spot ETFs.
In regards to where to safely store my crypto assets, I have never felt so lost and uncertain.
Last Friday, hackers looted approximately $6.3 billion from Binance, setting a record for the largest theft in cryptocurrency history. I did not rush to move my Bitcoin. Personally, I had no exposure to Binance assets, but I immediately verified whether my local Australian exchange was affected, thankfully everything remained secure.
I believe that under extreme pressure, the worst mistake people can make is acting in panic. Haste and fear lead to fatal misjudgments, an inherent human weakness hard to overcome. As the old saying goes: slow is smooth, and smooth is fast.
This is precisely why I wrote this article: to help investors plan their asset custody strategies and remain prepared, poised to handle any conceivable extreme scenario. Next, I will dissect each pathway for holding crypto assets, the potential risks they entail, and specific risk mitigation countermeasures for each threat.
Incident Review
The attackers breached Binance's hot wallet system—the infrastructure connected to the internet dedicated to processing daily user withdrawals. Binance officially stated that the intrusion began via a DevOps engineer's laptop compromised by hackers, with no current evidence of private key leakage. However, according to analysis by on-chain intelligence firm TRM Labs, the attackers actually needed no private keys at all, as they had already taken complete control of the core systems responsible for signing withdrawal instructions.
According to CoinDesk, the attackers embedded 50 pre-signed authorization instructions within a single transaction, all originating from the same Binance wallet and precisely matching every upcoming sequence number in its queue. This meant that regardless of which sequence number triggered next, the withdrawals were already pre-approved. TRM Labs monitoring shows that the vast majority of funds were drained in just around 20 minutes across 10 major blockchain networks.
Because centralized stablecoins have blacklist freeze capabilities, the thieves, desperate to launder the funds before Tether and Circle could intervene, paid premiums over 10% above market rates to forcibly swap portions of the assets into ETH on decentralized exchanges. Even so, within roughly 40 minutes of the largest single withdrawal, the issuers successfully froze approximately $1.8 billion in funds.
Figure: Timeline of on-chain movement and freezing of Binance's stolen funds
Within hours of the incident, Binance swiftly announced it would use its own capital to fully cover all losses. On October 31, the U.S. Federal Bureau of Investigation (FBI) officially identified the attack as the work of the notorious North Korean hacker group TraderTraitor. As of November 2, Binance had reopened deposit and withdrawal channels for 15 networks, including Bitcoin, and continued stress testing the remaining ones. Its full proof of reserves is expected to be published by Tuesday.
It is worth noting that the same hacker group targeted Bybit in February 2025, siphoning off roughly $1.5 billion, which set the previous historical high record until last Friday (per FBI data). That breach directly targeted a multi-sig cold wallet and occurred during what appeared to be a perfectly routine internal transfer. A post-incident report from Safe in March 2025 noted that the attackers tampered with the web frontend code used by signers, causing multi-sig approvers to see a benign transaction on screen while secretly approving a theft instruction instead. This demonstrates that multi-signatures only protect assets when every signer can genuinely and rigorously verify the underlying content being signed.
Both Custody Paths Suffer Major Blowbacks This Year
Not only are centralized institutions facing raids, but the self-custody route has also suffered severely this year. Since July, users of Coldcard and Ledger have cumulatively lost approximately $200 million; the former due to firmware vulnerability exploits, and the latter because distributors sold tampered devices with malicious hardware implants embedded. According to TRM Labs statistics through October 30, total stolen crypto assets across the industry in 2026 have reached $8.7 billion, making it the most severe year in history for asset security.
I possess extensive hands-on experience with both paths, whether dealing with full self-custody or holding substantial funds in regulated exchanges. I know their pros and cons intimately. The crux does not lie in picking a rigid side, but rather in deeply understanding the fatal weaknesses of each custody method and building impenetrable risk control barriers against them.
Risks and Risk Control Measures for Self-Custody
• Loss of Access: The Australian Taxation Office (ATO) noted on May 27, 2025, that cases of permanent loss of crypto assets due to SMSF trustees forgetting or losing passwords are common. Response: Store physical backups securely in an off-site, isolated location and prepare clear written recovery procedure guidelines for designated heirs.
• Mnemonic Phrase Phishing Scams: Fake physical mail impersonating official Ledger sources lures users into scanning QR codes and inputting mnemonic phrases (Cointelegraph, April 30, 2025). Response: Never input mnemonic phrases on any mobile device, computer, or website. Physical storage of mnemonic phrases must never connect to the internet.
• Supply Chain Tampered Devices: Individual distributors sold Ledger hardware wallets maliciously implanted with hardware Trojans, secretly intercepting the 24-word mnemonic phrases during the device's initial setup phase (The Block, October 13, 2026). Response: Must purchase directly from official hardware manufacturers; absolutely avoid third-party distributors.
• Firmware Vulnerabilities: Coldcard Mk4 faced exposed firmware flaws, which could allow attackers with physical device access to extract mnemonic seed phrases within 30 seconds (The Block, July 31, 2026). Response: Utilize multi-signature schemes, mixing hardware wallets from different manufacturers across distinct signing devices to eliminate reliance on a single firmware source.
• Burglary and Personal Threats: In Melbourne, a crypto investor was burglarized at home and forced to surrender $4 million AUD in cryptocurrency (The Age, August 18, 2025). Response: Configure additional passphrases and set up decoy wallets with fake balances; employ cross-regional multi-sig for core large holdings, ensuring a single individual cannot physically execute transfers locally.
• Unexpected Death of Trustees: Without meticulous planning, if a trustee passes away unexpectedly, their family will be entirely unable to access the assets, potentially sparking massive tax compliance disputes. Response: Establish legally binding crypto estate planning documents clearly delineating the designated roles of each private key holder.
The ultimate advantage of self-custody is: no intermediary can restrict your withdrawals, no third party can unilaterally misappropriate your funds, and there is absolutely zero risk of a bank-run-style collapse targeting centralized pooled funds.
But its most brutal cost lies precisely in this fact: you must bear 100% of every defensive risk control measure independently yourself. There is no customer service hotline to call, and once a mistake occurs, no one can help you recover a single cent.
Risks and Risk Control Measures for Exchange Custody
• Exchange Hack or Bankruptcy: As evidenced by last Friday's $6.3 billion Binance raid, and past collapses like FTX and Mt. Gox. Response: Prioritize strictly locally regulated, compliant licensed exchanges featuring independent client fund trust/segregation accounts, regular disclosure of complete audited proof of reserves, and adequate capital solvency.
• Account Takeover: Hackers breach personal accounts through SIM-swapping or credential-stuffing attacks. Response: Completely discard SMS verification codes, bind physical security keys such as YubiKeys as the sole two-factor authentication method, and enable whitelisted withdrawal address locks alongside delayed withdrawal protection mechanisms.
• Risk Control Account Freezes: Exchange anti-money laundering algorithms automatically trigger compliance freezes, locking accounts without warning and demanding cumbersome proofs of funds, sometimes spanning weeks or months. Response: Maintain reserve accounts across multiple distinct licensed compliant exchanges, distribute operating capital, and ensure redundant fiat deposit/withdrawal channels at all times.
• Regulatory Policy Shifts: Regulators order the halt of trading specific tokens or mandate forced withdrawal delistings. Response: Closely monitor regulatory dynamics in your jurisdiction and promptly migrate long-term core holdings to decentralized on-chain environments.
The explicit advantages of storing funds in top-tier exchanges are: operation is extremely convenient, supported by robust customer service systems, with ready-made fiat on/off-ramps. For institutions and trust funds requiring regular audits, their financial statements and tax receipts are highly standardized and transparent.
Yet its fatal weakness is equally well-known: what you essentially hold is merely a creditor IOU on the exchange's ledger. Your assets are directly exposed under the massive bullseye of systemic theft from centralized giant hot wallets.
What Changed My Perspective
For a long time, I adhered to a simple premise: as long as you enable YubiKey physical hardware tokens on your exchange account, bind strict withdrawal address whitelists, and only choose top-reputation compliant platforms, then centralized exchanges remain the safest and most hassle-free haven for ordinary investors.
But the disaster that unfolded at Binance last Friday completely shook and shattered this preconceived stance.
This was not an isolated account takeover caused by individual user security negligence. This involved the world's most capital-rich, technology-and-security-budget-heavy cryptocurrency exchange giant, whose underlying hot wallet withdrawal approval control flow was directly breached by hackers, resulting in $6.3 billion drained in merely 20 minutes.
Faced with such a massive breach of internal systems, even if a user maxes out all client-side security settings, they are utterly powerless.
Figure: Comparison of risks and control measures across different crypto asset custody solutions
Multi-Signature Mechanisms: A Compromised Middle Ground
Between full self-custody and pure exchange custody, does a middle ground exist that combines the advantages of both? The answer lies in collaborative multi-signature (Multi-sig) custody.
For individuals or self-managed funds (SMSFs), the most prevalent architecture is the 2-of-3 (two-out-of-three) model. For example, you personally hold two independent private keys, while a professional custodial service holds the third. Daily transfers are signed and executed using the two devices you hold, with the service provider stepping back; but if you accidentally lose one key, the provider can assist you in deploying a backup key to regain asset control after rigorous identity verification.
Below are the current mainstream multi-sig collaborative custody provider solutions on the market:
Figure: Architectural parameters and solutions of mainstream multi-sig collaborative custody providers
• Unchained: Employs a 2-of-3 architecture, with the Unchained team holding one key. Basic annual fees start around $250 USD; its core advantage lies in offering compliance solutions tailored specifically for SMSFs and family trusts, capable of issuing highly authoritative annual asset certificates to meet compliance audit standards.
• Casa: A classic 2-of-3 collaborative multi-sig framework, with the Casa team assisting in managing a backup key. Personal plan annual fee is roughly $250 USD, featuring an embedded digital inheritance module; however, their official website currently lacks explicitly listed exclusive product lines for SMSFs or institutional trusts.
• Nunchuk: Provides completely free autonomous DIY multi-sig tools, alongside assisted 2-of-3 solutions starting at $120. Distinguished by decentralized inheritance functionality via smart contract timelocks, allowing heirs to autonomously claim assets upon reaching the time threshold without requiring official Nunchuk intervention.
• Bitkey (by Block): Combines your mobile app, physical hardware device, and Block cloud servers into a 2-of-3 multi-sig setup. This is arguably the easiest multi-sig solution with the lowest entry barrier, retailing for approximately $400 AUD on the Australian official site, featuring a built-in 6-month timelock delayed inheritance mechanism; however, its user agreement strictly targets individuals and is not applicable to SMSF institutional funds.
• Sparrow: An open-source, completely free geek-grade desktop client. You must entirely rely on your own suite of hardware wallets to construct the multi-sig, with zero third-party custody involvement. This offers the highest level of technical control but presents the greatest challenge: you are solely responsible for safeguarding all key backups and the critical multi-sig configuration file (Wallet Configuration).
However, when it comes to self-managed superannuation funds (SMSFs), there is a rigid regulatory threshold: according to guidelines issued by the Australian Taxation Office (ATO) on October 24, 2025, crypto assets held by the fund must be stored in a dedicated wallet under the fund's independent name, and must be physically isolated from the trustee's personal assets; the fund's auditor must be able to clearly verify that the asset truly exists, unequivocally belongs to the fund, and is accurately valued. For pure self-custody, this means the trustee must use on-chain signed messages or initiate a controlled micro-test transfer, presenting the auditor with comprehensive custody policy documents that clearly stipulate the holder of each key and contingency plans for unexpected events or disputes (Bentleys, September 14, 2026).
As for who is qualified to hold keys, regulators have not yet imposed rigid, blanket restrictions. From my prudent perspective: if in a 2-of-3 architecture, two trustees each hold one key, they can independently complete legal signatures without external assistance, aligning closely with the ATO's compliance demands for the fund to maintain complete control over assets. Conversely, if every expenditure relies on an external third-party keyholder outside the trusteeship, the evidentiary basis for asset control becomes severely weakened. Regardless, final compliance requires the fund's auditor to verify item-by-item based on case-specific facts.
This is precisely the key dilemma preventing me from reaching a final conclusion today: I have not yet definitively chosen which absolutely trusted individual I am willing to entrust with that other critical signing device.
Alternative Pathway: Bitcoin Spot ETFs
Australia launched its Bitcoin spot ETFs starting in May 2022. Currently, at least six spot products are actively traded nationwide, with management fees generally ranging between 0.25% and 0.49% annually.
• Significant Advantages of Spot ETFs: Investors directly hold fund product shares rather than native Bitcoin tokens, thereby permanently eliminating concerns over lost private keys and mnemonic phrases. For SMSF funds, portfolio shares are directly calculated at fair value on June 30 annually based on official closing prices, making tax and audit reporting exceptionally streamlined, identical to holding standard publicly traded equities.
• Objective Drawbacks of Spot ETFs: Erosion from 0.45% annual management fees results in the underlying Bitcoin quantity represented by each share shrinking by roughly 4.4% after a decade. Furthermore, ETFs are only tradable during conventional stock exchange hours: for example, the Binance attack occurred at 6:05 AM Brisbane time last Friday, three full hours before the Australian Securities Exchange (ASX) opened. Critically, the vast majority of spot funds do not permit retail investors to redeem or withdraw physical Bitcoin, and more than 80% of the underlying assets for US Bitcoin and Ethereum ETFs are heavily concentrated within a single American custodian.
To be frank, I have never been a fervent fan of ETF products. However, following this year's relentless series of security black swan events, the allure of ETFs for investors seeking maximum convenience and compliance has indeed risen significantly. If an investor desires a completely hands-off, passive investment strategy, I fully comprehend their rationale for choosing ETFs. But please remain starkly aware: the underlying assets behind ETFs still require professional custodial institutions to manage, and these custodians remain physically vulnerable to hacking; according to disclosure documents from a certain US spot fund, neither the fund nor its sponsor provides full insurance coverage for the Bitcoin they safeguard.
Where My Current Asset Allocation Resides
As of now, the bulk of my crypto assets remain housed within a strictly regulated local centralized exchange. The core rationale behind this choice lies in the convenience of fund allocation, a transparent audit trail, and the straightforward, transparent tax reporting processed at fiscal year-end. Crucially, should I face unforeseeable accidental circumstances, my wife, who serves concurrently as a fund trustee, can seamlessly assume account control and access the funds without obstruction.
A Frank Truth
Every asset custody pathway listed in this article carries the potential for catastrophic failure. There simply does not exist an absolutely perfect panacea in this world; there are only the specific risk categories you consciously choose to endure, and the defensive measures you personally establish to hedge against those threats. This is merely my thoroughly deliberated analytical framework for the present moment, and absolutely not financial advice for anyone.
Slow Is Smooth, And Smooth Is Fast
I make it a habit to preemptively simulate and finalize critical macro decisions well before extreme pressure and black swan events truly materialize, ensuring that when storms suddenly erupt, I absolutely never need to panic into hasty choices. My logic for opening and adding to positions follows the exact same principle: trading plans must be drafted long before breaking news erupts, so that dark moments like those on Friday never disrupt my strategic footing.