---
title: Korean exchange Bithumb says an intruder spent an hour in its internal mobile groupware and took ID copies and resident registration numbers of 844 customers, plus data on 715 staff | ctxsec
url: https://ctxsec.com/items/bithumb-daouoffice-groupware-intrusion-844-customers-ids-exposed
description: ""
status: "official (Bithumb notice, Oct 29); cause still under investigation"
published: 2026-10-29
---

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[← Cybersecurity News](/news) · [markdown](/items/bithumb-daouoffice-groupware-intrusion-844-customers-ids-exposed.md)

official (Bithumb notice, Oct 29); cause still under investigation

2026-10-29

### Korean exchange Bithumb says an intruder spent an hour in its internal mobile groupware and took ID copies and resident registration numbers of 844 customers, plus data on 715 staff

Bithumb says an unauthorized outsider accessed its internal mobile groupware system, **DaouOffice**, from **11:28 AM to 12:27 PM KST on Oct 27** and removed stored personal data and files. It spotted the abnormal access at 12:14 PM, cut off the access path and suspended the system. It reported to KISA that night and to the Personal Information Protection Commission just after midnight.

- **Scope:** 6,444 customers in total; for 5,600 the data was encrypted and unreadable, while **844 customers** had readable data exposed: names, phone numbers, email addresses, resident registration numbers, driver's licence numbers, bank account numbers and ID copies. Also affected: **715 staff** (646 employees and 69 contractors).
- **Not affected (per Bithumb):** the groupware is separate from exchange accounts and asset data, and it has found no sign that the exchange or customer database was breached. It has stepped up monitoring of unusual trades and withdrawals.

**Watch for:** follow-on voice phishing and "Bithumb staff" impersonation using the leaked IDs. Bithumb says it never asks for passwords, OTPs or remote-control apps by phone, text or messenger. The case is also a reminder that groupware and HR systems often hold KYC copies that never belonged there.

Sources: [Bithumb notice: personal information leak of some customers and employees (Oct 29, Korean)](https://feed.bithumb.com/notice/1655458)