Microsoft has started to distribute important microcode updates for Intel processors powering systems running Windows 10 October 2018 Update or Windows Server 2019. The updates should protect the devices against L1TF and Spectre 3a/4 attacks.
Distribution of KB4465065 “Intel microcode updates”, has started through Windows Update and will only be installed on computers with specific Intel CPUs. These include many of the processors of the Skylake, Kaby Lake, Coffee Lake and Broadwell EP / EX generation. Also, systems needs at least Windows 10 with the October 2018 Update installed or run Windows Server 2019 to be eligible to receive the patches. Not all processor types in the mentioned CPU generations will be updated, Microsoft provides a full list of CPUs on its website.
Normally, main board vendors would need to release microcode patches. However, that would be a slow process with many companies involved. By making the UEFI updates available through the operating system, more systems will be patched faster.
The updates should protect computers against the L1TF attack and Spectre 3a/4 attacks. L1TF, also known as Foreshadow or L1 Terminal Fault, lets malicious software break into secure areas. This could result in attackers obtaining sensitive information such as cryptographic keys or passwords.
Spectre 3a and Spectre 4 are, amongst other Spectre variants, also known as Spectre NG. These Spectre attacks can be performed on both Intel and ARM CPUs, but do not work on AMD processors. With Spectre, attackers are able to trick a program into accessing arbitrary locations in the program’s memory space after which they can read the content of accessed memory. This could also result in disclosure of sensitive data.
The microcode updates can have a negative impact on performance of the system but this should be unnoticeable to most end users.