Microsoft 365 Alert – Service Degradation – Microsoft Defender XDR – Users may have been unable to access Threat Analytics in the Microsoft Defender XDR portal – RESOLVED

29/01/2026 08:50:00 AM

NHSmail Reference: INC46736432

Microsoft Reference: DZ1223715

Issue Status: RESOLVED

Issue Description: Users may have been unable to access Threat Analytics in the Microsoft Defender XDR portal.

Current Update: 29/01/2026 08:51:00 AM – Microsoft has determined that the cache infrastructure performance had fallen below suboptimal thresholds, and they applied manual mitigations to the affected portions of the infrastructure to relieve this impact. After a period of monitoring, they confirmed that the service returned to a healthy state.

Scope of impact: Any user attempting to access Threat Analytics in the Microsoft Defender XDR portal may have been impacted by this event

Root cause: The cache infrastructure performance fell below suboptimal thresholds, resulting in this impact.

Next steps: – Microsoft are reviewing the cache infrastructure to better understand what led to the error that resulted in impact and prevent similar future occurrences.