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Microsoft began implementing the new Intel countermeasure code against the Specter V3a, Specter V4, and L1TF vulnerabilities through Windows Update. Start with a patch for the latest version of Windows 10, the 1809 update version for October 2018 and Windows Server 2019.

Patch for Broadwell-E to Coffee Lake-S
The patch with the identifier KB4465065 addressed at the moment are only CPUs based on Skylake (-Y, -U, -H, -S, -D, -SP) Kaby Lake (Y, -U), a coffee Lake (-H , -S) and Broadwell (-E, -EP, -EX). Also for other versions of Windows 10 or earlier generations of Windows, the update is not yet available.

After installation, the countermeasures for the V3a and L1TF vulnerabilities are automatically activated, but not for Specter V4; here, users must activate by means of a manual intervention in the registry to activate this protection as well. The reason for this decision is likely to be the expected performance loss: Intel demands a performance of two to eight percent less on SYSmark 2014 SE and the SPEC integer test.

New microcode through Windows Update instead of BIOS

As a result of serious security vulnerabilities in the CPUs, Microsoft first distributed updates with a new microcode in April against the vulnerabilities of Specter V2 for Windows 10. The owners of the motherboards, for which the manufacturers had not yet provided a BIOS update with a new microcode, they could secure your system. Previous manual attempts to manually load the new microcode already released by Intel in Windows 10 failed.

Details of Specter V3a, V4 and L1TF

The 3a spectrum variant as a new version of "Meltdown" (variant 3) was discovered independently of Google's Project Zero and the Microsoft Security Response Center and was published in detail by ARM in May (PDF technical document). Those affected are the ARM Cortex-A15, -A57 and -72 cores, with ARM that classifies the risk that the attackers take advantage of the gap so low that countermeasures are not currently considered necessary. As with Meltdown, all Intel CPU architectures from the first generation core have been affected by this manufacturer.

Specter Variant 4 (white paper) was discovered in Google's Project Zero. Like Specter's Variant 1, this vulnerability can be connected to the customization of applications, since existing Specter V1 measures also benefit Specter V4. However, to prevent the breach from being exploited by other means, Intel and Partners have also decided to readjust the microcode of the CPU. It also contains countermeasures against variant 3a, which do not cost performance. Variation 4 affects AMD, ARM, IBM and Intel.

L1 Terminal Fault (L1TF) again comprises three vulnerabilities that represent especially for virtual machines and services in the cloud at high risk because they allow attackers to leave their own instance and access data from another virtual machine.


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