Bithumb, South Korea's second-largest crypto exchange by volume, said an outside party broke into the internal mobile system its staff use for work and messaging, and that personal information was taken. The exchange found the intrusion on Tuesday, Oct. 27 and notified the Korea Internet & Security Agency and the Personal Information Protection Commission. As of Asian afternoon hours on Oct. 28, no loss of crypto funds had been reported.
What Bithumb has and has not said
Bithumb says the breached system runs separately from its trading platform, so customer virtual assets cannot be reached through it. It is still working out the exact scope, including whether member data was involved. An industry source said some customer personal information did leak, but the exchange has not confirmed a figure.
Plenty remains open: how many people are affected, what kind of data was taken, whether deposits and withdrawals were disrupted, and how the attacker got in. The exchange has not said how the system was accessed.
Two other Korean financial firms reported incidents the same day. Brokerage Daishin Securities said names, emails and phone numbers of 38,490 customers leaked after an outside attack, while asset manager Mirae Asset Global Investments said it blocked abnormal access to some web systems and that investor data was untouched. The Financial Supervisory Service is assessing all three cases.
Context: a wave of attacks and a rough year for Bithumb
The regulator's governor said cyberattacks had hit 16 South Korean financial firms as of mid-October, and officials earlier put the number of leaked records at around 100,000. Authorities have also urged website operators to check for a recently disclosed PHP flaw that lets attackers run commands on a server without logging in, although nothing links it to the Bithumb case yet.
It is the second time this year that Bithumb's internal controls have come under scrutiny. In February it mistakenly credited customers with 620,000 BTC instead of 620,000 won during a promotion, worth about $40 billion at the time; the balances existed only on its internal ledger and the exchange says it recovered 99.7%. In March, the country's financial intelligence unit fined it 36.8 billion won over anti-money-laundering failures.
Also on Oct. 28, Coinbase said an incident at analytics vendor Amplitude exposed contact details for a small subset of customers, while insisting its own systems were not breached and funds were unaffected. Changpeng Zhao listed all four incidents in a post, warning that leaked exchange data is mostly used for phishing, SIM swapping and social engineering.
What to watch next
Watch for a final tally of exposed data, any compensation from Bithumb, and the outcome of the regulator's inspection. The episode also adds pressure on the exchange's plan to list its shares in 2028.
What it means for traders
For futures traders, the key point is that this is not a loss of funds: no withdrawals of assets have been reported, and the exchange says the breached system is isolated from trading. That means no sign yet of the liquidity shock that follows a hot-wallet hack, which usually brings sharp moves and cascading liquidations.
The practical risk is personal data. Leaked emails, phone numbers and account details are typically used for impersonation scams and SIM swaps, so exchange users may want an authenticator app instead of SMS codes, anti-phishing codes where offered, and withdrawal whitelists. More on exchange security in our exchange rankings.
On the market side, Bitcoin was trading near $81,000 ahead of the Fed decision, and a data incident at a regional exchange was not cited as a price driver. The signal that would matter for open positions is whether Bithumb restricts deposits or withdrawals.