mirror of
https://github.com/LOLBAS-Project/LOLBAS
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40 lines
2.1 KiB
YAML
40 lines
2.1 KiB
YAML
---
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Name: Fsi.exe
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Description: 64-bit FSharp (F#) Interpreter included with Visual Studio and DotNet Core SDK.
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Author: Jimmy (@bohops)
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Created: 2021-09-26
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Commands:
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- Command: fsi.exe c:\path\to\test.fsscript
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Description: Execute F# code via script file
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Usecase: Execute payload with Microsoft signed binary to bypass WDAC policies
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Category: AWL Bypass
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Privileges: User
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MitreID: T1059
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OperatingSystem: Windows 10 2004 (likely previous and newer versions as well)
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- Command: fsi.exe
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Description: Execute F# code via interactive command line
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Usecase: Execute payload with Microsoft signed binary to bypass WDAC policies
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Category: AWL Bypass
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Privileges: User
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MitreID: T1059
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OperatingSystem: Windows 10 2004 (likely previous and newer versions as well)
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Full_Path:
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- Path: C:\Program Files\dotnet\sdk\[sdk version]\FSharp\fsi.exe
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- Path: C:\Program Files (x86)\Microsoft Visual Studio\2019\Professional\Common7\IDE\CommonExtensions\Microsoft\FSharp\fsi.exe
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Code_Sample:
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- Code: https://gist.github.com/NickTyrer/51eb8c774a909634fa69b4d06fc79ae1
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Detection:
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- Elastic: https://github.com/elastic/detection-rules/blob/414d32027632a49fb239abb8fbbb55d3fa8dd861/rules/windows/defense_evasion_unusual_process_network_connection.toml
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- Elastic: https://github.com/elastic/detection-rules/blob/414d32027632a49fb239abb8fbbb55d3fa8dd861/rules/windows/defense_evasion_network_connection_from_windows_binary.toml
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- BlockRule: https://docs.microsoft.com/en-us/windows/security/threat-protection/windows-defender-application-control/microsoft-recommended-block-rules
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- IOC: Fsi.exe execution may be suspicious on non-developer machines
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- Sigma: https://github.com/SigmaHQ/sigma/blob/6b34764215b0e97e32cbc4c6325fc933d2695c3a/rules/windows/process_creation/proc_creation_win_lolbin_fsharp_interpreters.yml
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Resources:
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- Link: https://twitter.com/NickTyrer/status/904273264385589248
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- Link: https://bohops.com/2020/11/02/exploring-the-wdac-microsoft-recommended-block-rules-part-ii-wfc-fsi/
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Acknowledgement:
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- Person: Nick Tyrer
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Handle: '@NickTyrer'
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- Person: Jimmy
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Handle: '@bohops'
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