Microsoft Warns: New Windows ISOs Need Updated Defender Definitions Before Use
Microsoft has released a critical Microsoft Defender update for Windows installation images, urging users to apply it before deploying fresh installations of Windows 11 , Windows 10 , or Windows Server systems.
When setting up a new Windows OS from an ISO image, there’s often a temporary security gap — the built-in Defender definitions may be outdated, leaving the system vulnerable during early setup. To close this window of risk, Microsoft has pushed out updated security intelligence via version 1.429.122.0 , which includes vital protections against emerging threats like the Lumma infostealer , known to affect hundreds of thousands of PCs globally.
This update applies to:
- Windows 11
- Windows 10 (Home, Pro, Enterprise)
- Windows Server 2016, 2019, and 2022
The package brings the following key updates:
- Platform version: 4.18.25040.2
- Engine version: 1.1.25040.1
- Security intelligence version: 1.429.122.0
In addition to defending against Lumma, this update adds detection rules for various backdoors, trojans, and other malware strains.
Microsoft strongly recommends applying this update before deployment , especially for users upgrading to Windows 11 24H2 , as recent changes to minimum CPU requirements make using updated images even more important.
