Bithumb Confirms Data Breach Exposing 844 Customers’ Details and 715 Staff Records

Highlights:

• Bithumb confirmed a data breach that exposed the personal information of 844 customers and 715 employees and contractors.
• The exchange said another 5,600 customer records were involved, but their encrypted data remained unreadable.
• Bithumb found no evidence of trading platform access and warned customers about possible phishing scams.

South Korean cryptocurrency exchange Bithumb has confirmed that a cyberattack on its internal work system exposed the personal information of 844 customers and 715 employees and contractors. The company said it also took records related to another 5,600 customers, but they remained encrypted and unreadable.

In an October 29 official notice, Bithumb said an unauthorized person had accessed its mobile office system on October 27. The exchange first identified employee data in the leak, then confirmed that some customer information was also included.

Bithumb Details Internal System Breach: 6,444 Customers and 715 Employees Compromised

South Korea's second-largest crypto exchange, Bithumb, disclosed that an unauthorized external intrusion into its internal corporate groupware (DaouOffice) for approximately one hour on October… pic.twitter.com/pl2sHQoVt5

— Wu Blockchain (@WuBlockchain) October 29, 2026

Bithumb Says 6,444 Customer Records Were Involved

According to Bithumb, the incident involved information belonging to 6,444 customers. The company said it had encrypted the records of 5,600 customers, preventing anyone from reading them. However, the attackers exposed personal information belonging to the remaining 844 customers. The leaked records included names, mobile phone numbers, email addresses, national identification numbers, driving license numbers, bank account numbers and copies of identity documents. Bithumb did not specify whether every affected customer had all these details exposed.

The attack also affected 715 people connected to the company, including 646 employees and 69 contractors or other outside personnel. Bithumb has already contacted these workers and plans to notify affected customers individually by text message. The company has also added a feature to its official website that allows users to check whether the breach affected their personal information.

Attackers Accessed Bithumb’s Internal System on October 27

Bithumb said the intruder accessed its mobile groupware system, Daou Office, from 11:28 a.m. to 12:27 p.m. local time on October 27. During that period, the attacker copied personal information and files stored in the system without authorization. The company detected unusual access at 12:14 p.m. and began blocking the entry route. It also suspended the mobile groupware service and assembled a team to investigate the breach with the software provider.

Bithumb reported the incident to the Korea Internet & Security Agency at 11:39 p.m. on October 27. It notified the Personal Information Protection Commission at 12:48 a.m. the following day.

The exchange said the breached office system operated separately from trading accounts and customers’ asset records. It found no evidence that attackers directly accessed its trading platform or customer database. Bithumb did not report any cryptocurrency theft or loss of customer funds. The exchange has increased monitoring of suspicious trades and withdrawals as a precaution.

Bithumb Warns Customers About Fraud Risks

The firm warned customers about phishing messages and calls from scammers pretending to be company employees. It said criminals could use the stolen information to trick users into sharing account details or sending money.

The exchange advised customers not to share passwords, verification codes or other sensitive information. It also warned them against installing unknown apps, changing withdrawal addresses or transferring funds at someone else’s request. Bithumb will guide customers whose identity documents were exposed on replacing their IDs and checking for identity theft.

The company also guaranteed support and compensation for losses that are confirmed, subject to the circumstances and applicable laws. Bithumb is still working on the attack’s method and is going to improve its security system.