New Update Security Intelligence Updates in Microsoft Defender (Threat Detection Changelog)

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September-2025 (Platform: 4.18.25090.3009 | Engine: 1.1.25090.3001)

  • Security intelligence update version: 1.439.345.0
  • Release date: September 8, 2025 (Engine) / September 21, 2025 (Platform)
  • Platform: 4.18.25090.3009
  • Engine: 1.1.25090.3001
  • Support phase: Security and Critical Updates

What's new​


  • Improved service startup behavior: The core service now only restarts when necessary, for example, during a successful platform update. This change allows the organization to avoid unnecessary restarts when the service is already running correctly.
  • Improved stability for RPC services: Added input validation across multiple RPC endpoints to prevent crashes caused by malformed data, which addresses a reported security vulnerability.
  • Fixed threat exclusion handling: Resolved an issue where severity-based exclusions could cause the engine to misidentify threats, potentially skipping high severity detections.
  • Restored performance optimization for network file access: Fixed a regression that caused slowdowns during file operations, like robocopy to network shares. The fix included reintroducing the logic to skip unnecessary checks on non-local files when Controlled Folder Access is enabled.
 

October-2025 (Platform: 4.18.25100.9008 | Engine: 1.1.25100.9002)​

  • Security intelligence update version: 1.441.131.0
  • Release date: November 6, 2025 (Engine) / November 17, 2025 (Platform)
  • Platform: 4.18.25100.9008
  • Engine: 1.1.25100.9002
  • Support phase: Security and Critical Updates

What's new​


  • Fixed Network Inspection Service stability issue: The service now correctly restarts when memory usage exceeds the threshold, which prevents the service from getting stuck in a faulty or pending state.
  • Reduced startup delay for Antimalware Service: Improved Defender service startup time by removing its dependency on Core Service startup. This change improves overall system startup performance.
  • Fixed crash in Defender settings on x86 devices: Corrected an issue that caused the system to crash when applying Defender configuration settings on 32-bit machines.
  • Fixed Defender startup issue: The platform no longer crashes when processing invalid Attack Surface Reduction rule exclusions.
  • Reduced system resource usage: Defender no longer generates excessive Data Loss Prevention (DLP) logs that caused high disk activity, improving overall performance and stability.
Microsoft Defender Antivirus security intelligence and product updates - Microsoft Defender for Endpoint
 
November-2025 (Platform: 4.18.25110.6 | Engine: 1.25110.1)
  • Security intelligence update version: 1.443.6.0
  • Release date: December 11, 2025 (Engine) / December 17, 2025 (Platform)
  • Platform: 4.18.25110.6
  • Engine: 1.1.25110.1
  • Support phase: Security and Critical Updates

What's new​

  • Performance improvements when querying WMI due to Behavior Monitor detections.
  • Fixed potential hang in PowerShell on Server 2016 due to Defender Filter Driver.
  • Resolved an application compatibility issue due to a loopback with SMB1 enabled.
  • Fixed issue with ASR path exclusion requiring additional "" characters to function appropriately.
  • Resolved high I/O issue with NisSrv.exe due to high volume of network logging events.
  • Fixed error in threat enumeration causing repeated failure notifications every 15 minutes in SCCM.
  • Improved drive mapping enumeration for devices with many drives which resulted in false positive detections for ASR rules.
  • Fixed a crash with Defender related to long scan times causing the service to hang in Windows Server 2019
Microsoft Defender Antivirus security intelligence and product updates - Microsoft Defender for Endpoint