Coinbase Outlines Cold Storage Defense After Binance Hack

TLDR

Coinbase says it stores more than 99% of customer cryptocurrency in offline cold wallets.
Coinbase reports that the $6.34 billion Binance hack did not affect its systems or customer funds.
Binance reported freezing or intercepting approximately $2.85 billion and replenishing 98% of affected token assets.
Coinbase reported $376.6 billion in assets on its platform as of September 30, 2026.
South Korean regulators urged cryptocurrency exchanges to increase cold storage holdings beyond the existing 80% legal requirement.

Coinbase says it keeps more than 99% of customer crypto in cold storage after Binance’s $6.34 billion hack on October 29. Cold wallets limit online access. Coinbase says the breach left its systems and customer funds untouched. The theft raised questions about transfer approvals.
Coinbase Details Its Cold Storage Safeguards
Coinbase stores most customer holdings offline and keeps balances online to handle withdrawals. It says controls protect transfers, including spending limits, unusual-activity checks and the ability to stop transaction approvals.
The exchange also splits signing keys across different systems. No single person or machine holds a complete key. Coinbase says it keeps customer assets backed one-to-one and does not lend them without permission. New York regulators oversee its custody business.
Binance Hack Exposes Withdrawal Approval Risks
Binance said attackers accessed its wallet-signing service after compromising employee computers through malicious downloads and a fake job interview. Its account of the October attack describes how stolen credentials helped hackers move funds outside normal withdrawal procedures.
The exchange said about $2.85 billion had been frozen or intercepted by November 3. It reported replenishing 98% of affected token assets and pledged to cover customer losses.
The incident involved transaction permissions rather than a reported theft of private keys. Offline storage alone cannot prevent abuse of an authorized signing process.
Other Exchanges Face Similar Security Questions
Brazil’s Mercado Bitcoin reported a November 2 attack involving about $38 million. Its plan to cover customer losses followed suspicious transfers across several blockchains.
Coinbase reported $376.6 billion in assets on its platform at September’s end. Its filing listed $8.6 billion in company cash and $2.2 billion in investment crypto, apart from customers’ holdings.
Research estimates that Coinbase safeguards roughly 84% of US spot Bitcoin ETF assets. Coinbase said a 2025 support-agent data breach could cost up to $400 million.
South Korea Reviews Offline Wallet Rules
South Korea’s financial regulator urged exchanges to hold more crypto offline after the Binance breach. Existing rules require at least 80% in cold storage, while Upbit reported 99.17% at September’s end.
As Binance reopened services, it warned users about withdrawal scams, including offers to speed up transfers for a fee. Holding more funds offline can slow access. Bithumb customers faced withdrawal delays exceeding 13 hours in August when online wallet balances ran low.
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