Muddled Libra

Attackers Abuse Legitimate Microsoft Defender Exclusions to Conceal Malware

Huntress researchers have detailed an evasion technique in which threat actors avoid disabling Microsoft Defender entirely. Instead, they create targeted exclusions for specific folders or file extensions, allowing malware to operate undetected while the protection status remains apparently active. These exclusions are configured through PowerShell commands, Windows Management Instrumentation, Group Policy, or direct registry modifications, all requiring administrator privileges after initial compromise. A registry key named HideExclusionsFromLocalAdmins can further conceal the list of exclusions from local administrators viewing the interface. The approach has been linked to campaigns involving GootKit in 2019, WhisperGate in 2022 that excluded the entire C: drive, and Muddled Libra in 2024. Defenders are advised to monitor registry changes directly, as this bypasses interface hiding, and to flag exclusions of entire drives or common directories such as temporary and downloads folders.