Nikkei Inc., owner of the Financial Times and publisher of the Nikkei 225 stock index, confirmed attackers stole credentials and accessed its internal Slack workspace after malware infected an employee's personal computer. The breach exposed names, email addresses, and internal chat histories of 17,368 employees and business partners. What's interesting: once attackers had valid Slack tokens, they scraped private messages and profile information at scale without triggering strong anomaly detection. Security researchers note the attack highlights a fundamental visibility gap. As Mayank Kumar of DeepTempo explained, "For a SIEM, the login was valid, so no rule would fire. For an NDR, the traffic was encrypted, making payload inspection impossible." The attackers blended into normal traffic patterns while exfiltrating relationship maps, sensitive discussions, and contact intelligence that fuels future BEC and phishing campaigns. Slack's role as both messaging fabric and identity surface means compromised credentials provide broad access to communications data. This isn't Nikkei's first security incident—the company lost approximately $29 million in September 2019 to a Business Email Compromise scam. The current breach underscores how collaboration platforms have evolved into secondary identity and data hubs. While Nikkei reports no compromise of journalistic sources or editorial content, the exposed data set still includes private communications and contact information for staff and external partners that can be weaponized for targeted social engineering and extortion.
🎯CORTEX Protocol Intelligence Assessment
Business Impact: Nikkei Slack data breach underscores how theft of collaboration data exposes organizations to reputational harm, targeted social engineering, and long-lived privacy risk for employees and partners. Media and financial-sector entities that rely on chat tools for coordination may see trust erode if private discussions and contact networks are weaponized by attackers. Technical Context: The breach originated from a malware-compromised personal device, where stolen credentials were reused to access Nikkei's internal Slack workspace without triggering strong anomaly detection. Slack's role as both messaging fabric and identity surface means that once attackers gain valid tokens, they can blend into normal traffic patterns while exfiltrating large volumes of messages and profile data.
⚡Strategic Intelligence Guidance
- Enforce multi-factor authentication and device posture checks for all Slack and collaboration-tool access, blocking logins from unmanaged or non-compliant endpoints where feasible.
- Integrate collaboration platforms into SIEM and UEBA monitoring, with detections for unusual export patterns, large history downloads, or abnormal API calls associated with single user accounts.
- Implement strict offboarding and access review processes that regularly validate which external partners and contractors retain Slack access and prune unused accounts.
- Update security awareness training to highlight the sensitivity of chat data, emphasizing that internal channels may be harvested and reused in targeted phishing and extortion campaigns.
Threats
Data breachCredential theftChat data scraping
Targets
Nikkei employeesNikkei business partners
Impact
Data Volume:17,368 affected accounts and Slack message histories