Bithumb breached through the system its staff message on

Bithumb, the second-largest crypto exchange in South Korea, found on Tuesday that an outsider had been inside the internal mobile system its staff use to work and message each other. The intruder took personal information with them. The exchange notified the Korea Internet and Security Agency and the Personal Information Protection Commission, and told Yonhap it is still working out the scope, including whether member data is in it.

“I understand that major financial investment companies experienced overall hacking incidents yesterday.”

— Lee Chan-jin, governor of the Financial Supervisory Service, https://www.coindesk.com/tech/2026/10/28/bithumb-hacked-through-employee-system-as-south-korean-financial-firms-face-cyberattacks

No coins are reported missing. Bithumb says the breached system sits apart from the trading platform, so customer assets could not be reached through it. What it has not said is how many people's data was exposed, which categories of data, or whether deposits and withdrawals were touched. Those three answers come days after the first statement, when they come at all.

One firm every 0.81 days

Bithumb is one name on a longer list this week. South Korea's Financial Supervisory Service said on Wednesday it is assessing three financial firms, Bithumb among them. Daishin Securities reported that personal and credit information for 38,490 customers leaked in an outside attack. Mirae Asset Global Investments said it blocked abnormal access to some web systems and that investor information was untouched.

FSS governor Lee Chan-jin said earlier this month that cyberattacks had reached 16 South Korean financial firms as of 14 October. Thirteen days, sixteen firms: one every 0.81 days through the first half of the month. Fourteen days have passed since that count, and three more names surfaced this week.

The exchange that once credited 620,000 BTC

Bithumb has been here before, and the February version was arithmetic rather than intrusion. That month it credited customers with 620,000 BTC instead of 620,000 won. At today's prices the won figure is $467 and the bitcoin figure is $50.3bn, so the slip inflated the amount by a factor of roughly 108 million. The chief executive put it down to weak internal control at the time.

If you keep a balance on an exchange, the reading we set out in our guide to keeping crypto safe applies here: your balance is a claim against the platform, and the claim is worth what the platform's operations are worth. Nobody opened the vault this week. They opened the app the staff keep on their phones, and that turned out to be enough to take something.

Informational material, not investment advice. The scope of the Bithumb breach has not been established, no loss of customer assets has been reported, and the rate of attacks and the February conversion are our own arithmetic on the published figures at prices on 28 October 2026.