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MediumSigmaHQ Christopher Peacock @securepeacock +1

Use of FSharp Interpreters

Detects the execution of FSharp Interpreters "FsiAnyCpu.exe" and "FSi.exe" Both can be used for AWL bypass and to execute F# code via scripts or inline.

Detection logic

Detection requirements

Platform: Containers ESXi IaaS Identity Provider Linux macOS Network Devices Office Suite SaaS Windows
The rule states no platform. This is derived from the ATT&CK technique it maps to.
Log source product: windows
Log source category: process_creation

Known benign triggers

Legitimate use by a software developer.

References

Links the source published beside this detection. Reference is the link the source wrote, unmodified. Class is decided by this catalogue from the host and path, not stated by the source. Cited by counts published detections citing the same resource, including this one, and the sources beneath it count the repositories this catalogue ingests, which is not the same as independent research.
Reference	Class	Cited by
bohops.com/2020/11/02/exploring-the-wdac-microsoft-recommended-block-rules-part-ii-wfc-fsi/	Security research	Only this detection cites it
learn.microsoft.com/en-us/windows/security/application-security/application-control/windows-defender-application-control/design/applications-that-can-bypass-wdac	Product documentation	3
lolbas-project.github.io/lolbas/OtherMSBinaries/Fsi/	Tool	Only this detection cites it
lolbas-project.github.io/lolbas/OtherMSBinaries/FsiAnyCpu/	Tool	Only this detection cites it

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