Answering my own Question #1: Looks like it sets values for FeatureSettingsOverride and FeatureSettingsOverrideMask under the "HKEY_LOCAL_MACHINE\SYSTEM\Curren

Answering my own Question #1: Looks like it sets values for FeatureSettingsOverride and FeatureSettingsOverrideMask under the "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management" registry key. FeatureSettingsOverride is a bit field where bit 0 controls the mitigation for CVE-2017-5715 (Spectre) and bit 1 controls it for CVE-2017-5754 (Meltdown). If the bit value is 0 the corresponding mitigation is enabled, if 1 it's disabled. FeatureSettingsOverrideMask is simply a mask to control which bits of FeatureSettingsOverride to apply. So, for example, FeatureSettingsOverride = 2 and FeatureSettingsOverrideMask = 3 would enable the Spectre mitigation (if available) and disable the Meltdown one. More info here: https://support.microsoft.com/en-us/topic/windows-server-guidance-to-protect-against-speculative-execution-side-channel-vulnerabilities-2f965763-00e2-8f98-b632-0d96f30c8c8e https://support.microsoft.com/en-us/topic/windows-server-gui... https://gist.github.com/daBONDi/6f86210e54c68e84e85372fc4d1f0d82 https://gist.github.com/daBONDi/6f86210e54c68e84e85372fc4d1f... Haven't checked if the program emits different behavior for other CPU's or OS versions.