What to Do When a Data Breach from Unauthorized Access Occurs: Immediate Steps and Preventing Recurrence

The article, set against a backdrop of repeated unauthorized access incidents and personal data leaks targeting companies since around September 2026, organizes concrete response procedures to follow when a data breach has been confirmed. In the initial phase it emphasizes first “isolating the system” to prevent further leakage, and prioritizing the “preservation of evidence” such as access logs that show intrusion traces.

Next, it calls for organizing the facts using the 5W1H framework and reporting or consulting with the police, cyber-consultation desks, and industry-specific regulatory authorities. It also states that notifications on the company’s website and to affected users must be made in accordance with the Personal Information Protection Commission’s rules.

As mid- to long-term measures after emergency response, the article recommends establishing a response office to ascertain the full scope of damage and consider measures to prevent secondary harm, and to create and operate recurrence-prevention measures. As concrete examples it lists nine items including software updates, permission settings, WAF/IPS deployment, and two-factor authentication.

Furthermore, to guard against secondary damage (such as impersonation and unauthorized login), the article encourages introducing fraud-detection services. The provider’s O-PLUX performs real-time screening using device identification, IP analysis, bot detection, and negative-list checks, and claims to be “No.1 domestically with more than 120,000 site deployments.” The article emphasizes both rapid initial actions and subsequent organizational measures, as well as the use of external services.