{"id":"b96b2031-7c17-4473-afe7-a30ce714db29","title":"Use of FSharp Interpreters","description":"Detects the execution of FSharp Interpreters \"FsiAnyCpu.exe\" and \"FSi.exe\"\nBoth can be used for AWL bypass and to execute F# code via scripts or inline.\n","author":"Christopher Peacock @SecurePeacock, SCYTHE @scythe_io","status":"test","level":"medium","date":"2022-06-02","modified":"2024-04-23","tags":["attack.execution","attack.t1059"],"technique_ids":["T1059"],"logsource":{"category":"process_creation","product":"windows"},"falsepositives":["Legitimate use by a software developer."],"references":["https://learn.microsoft.com/en-us/windows/security/application-security/application-control/windows-defender-application-control/design/applications-that-can-bypass-wdac","https://bohops.com/2020/11/02/exploring-the-wdac-microsoft-recommended-block-rules-part-ii-wfc-fsi/","https://lolbas-project.github.io/lolbas/OtherMSBinaries/FsiAnyCpu/","https://lolbas-project.github.io/lolbas/OtherMSBinaries/Fsi/"],"source_path":"rules/windows/process_creation/proc_creation_win_fsi_fsharp_code_execution.yml","source_sha256":"bef3302765f6b2bb6e29b89aecb9a2279ae2f3c9e3587d692db7650a4f5c1f18","source_url":"https://github.com/anpa1200/sigma/blob/b249e9683190cffdcaf188ccbfb90bf4759844e1/rules/windows/process_creation/proc_creation_win_fsi_fsharp_code_execution.yml","license":"Detection Rule License 1.1","license_url":"https://github.com/SigmaHQ/Detection-Rule-License/blob/main/LICENSE.Detection.Rules.md","yaml":"title: Use of FSharp Interpreters\nid: b96b2031-7c17-4473-afe7-a30ce714db29\nstatus: test\ndescription: |\n    Detects the execution of FSharp Interpreters \"FsiAnyCpu.exe\" and \"FSi.exe\"\n    Both can be used for AWL bypass and to execute F# code via scripts or inline.\nreferences:\n    - https://learn.microsoft.com/en-us/windows/security/application-security/application-control/windows-defender-application-control/design/applications-that-can-bypass-wdac\n    - https://bohops.com/2020/11/02/exploring-the-wdac-microsoft-recommended-block-rules-part-ii-wfc-fsi/\n    - https://lolbas-project.github.io/lolbas/OtherMSBinaries/FsiAnyCpu/\n    - https://lolbas-project.github.io/lolbas/OtherMSBinaries/Fsi/\nauthor: Christopher Peacock @SecurePeacock, SCYTHE @scythe_io\ndate: 2022-06-02\nmodified: 2024-04-23\ntags:\n    - attack.execution\n    - attack.t1059\nlogsource:\n    category: process_creation\n    product: windows\ndetection:\n    selection:\n        - Image|endswith:\n              - '\\fsi.exe'\n              - '\\fsianycpu.exe'\n        - OriginalFileName:\n              - 'fsi.exe'\n              - 'fsianycpu.exe'\n    condition: selection\nfalsepositives:\n    - Legitimate use by a software developer.\nlevel: medium\n","validation":"yaml_parsed_not_backend_compiled_or_live_validated","techniques":[{"key":"enterprise/T1059","id":"T1059","name":"Command and Scripting Interpreter","page":"techniques/enterprise/T1059/"}],"data_path":"data/detection-rules/b96b2031-7c17-4473-afe7-a30ce714db29.json","kind":"sigma"}