NTT Communications Suffers Data Breach Impacting 18,000 Companies

NTT Communications (NTT Com) has disclosed a data breach affecting nearly 18,000 corporate customers after discovering unauthorized access to its internal systems.

The company detected the intrusion on February 5, 2025, and confirmed the potential data leak the following day.

The breach was identified by NTT Com's information security department, which detected unusual log activity on an internal system known as the Order Information Distribution System — a platform used for managing service activations and modifications.

Upon detecting the anomaly, the company took initial containment measures by restricting access to the affected system on the same day. Further investigation revealed that some corporate customer data may have been exfiltrated. By February 15, the security team identified a second compromised device within the internal network and immediately disconnected it to prevent further unauthorized access.

NTT Communications is a subsidiary of Nippon Telegraph and Telephone Corporation (NTT), one of Japan’s largest telecommunications companies. It provides cloud, network, and data center services to businesses worldwide, making it a key player in Japan’s corporate IT infrastructure. The breach, while limited to corporate clients, raises concerns about the security of critical enterprise services.

According to the company's statement, the leaked data includes:

• Customer contract numbers
• Corporate names and contact persons
• Telephone numbers and email addresses
• Physical addresses
• Service usage details

NTT Com confirmed that the breach does not involve personal consumer data, nor does it affect corporate mobile contracts from NTT Docomo. At present, there is no evidence that the stolen data has been misused. The company has begun notifying affected customers through direct communication methods such as letters and sales representatives, clarifying that no notifications will be sent via email to prevent phishing risks.

In response to this incident, NTT Com is reinforcing its security posture by enhancing monitoring systems and implementing additional protective measures to prevent recurrence. The company also pledged to disclose further findings if new information emerges.

This incident comes just two months after another cyberattack on NTT Group, when its subsidiary, NTT Docomo, suffered a massive Distributed Denial-of-Service (DDoS) attack, disrupting services for nearly 12 hours. The recurrence of security incidents highlights ongoing cybersecurity challenges for Japan’s largest telecom provider.