Sign in to your XDA account

Summary
- New Microsoft Defender update boosts security for old Windows ISOs
- Latest update includes improved Defender software binaries for better protection
- Package must be applied offline to specific Windows versions for enhanced security
Microsoft keeps encouraging users to install the latest version of Windows, or at least get ones that are still eligible to get monthly security updates. In addition to new features, one of the reasons behind this is that the latest updates include fixes for newly discovered security threats and vulnerabilities. However, things can be a bit tricky with fresh Windows installs using ISOs.

Related
5 things you may already be doing that compromise your Windows security
There's no absolute way to protect your PC from security threats. However, there are some habits you should definitely get rid of ASAP.
The problem with Windows ISOs is that the older they get, the more is the likelihood of them making your system vulnerable upon deployment. This is because those old Windows images don't include the latest security updates, making your PC vulnerable until you download them via Windows updates or apply them directly to the ISO. There is one more issue with old Windows images and that's "outdated antimalware software binaries." Now, Microsoft is trying to fix it by releasing a new Microsoft Defender update (package version 1.429.122.0) for Windows installation images.
Latest Microsoft Defender binaries will improve the security of old Windows images

Old Windows ISOs include old Microsoft Defender binaries, which don't give you the best protection against threats until they receive what Microsoft calls "the first anti-malware software update." The latest Microsoft Defender update wants to address this protection gap in new deployments: you don't have to risk your PC momentarily while the anti malware software installs.
The new Defender update include the latest Microsoft Defender software binaries, which not only helps Windows' built-in antivirus tool but are also helpful to another security solution that you may have, as per Microsoft's support document. The latest antimalware update packages for Microsoft Defender must be applied to WIM and VHD Windows Installation files offline for the following versions of Windows:
- Windows 11
- Windows 10 (Enterprise, Pro, and Home editions)
- Windows Server 2022
- Windows Server 2019
- Windows Server 2016
The latest Defender package version updates the anti-malware client and anti-malware engine, and they're all important and are used by Microsoft Defender Antivirus in Windows 11. The package size can differ based on the type of platform you use. It's 78.2 MB for ARM64, while the sizes are 128 MB and 132 MB for x86 and x64 systems, respectively.
To apply this update, you'll need to run a 64-bit Windows 10 or a later and have PowerShell 5.1 or later with Microsoft.Powershell.Security and DISM modules installed. You can follow this easy guide on Microsoft's website to apply the package on your Windows installation images. According to Microsoft, you should follow a three-month update frequency routine.