Suspicious Csi.exe Use (via process_creation)

title: Suspicious Csi.exe Use (via process_creation)
id: eeab7e95-96e5-5b2f-bae0-34fdb1273a29
status: stable
description: This rule detects Csi.exe is a signed binary from Microsoft that comes with Visual Studio and provides C# interactive capabilities. It can be leveraged to run C# code from a file passed as a parameter in command line. Early version of this utility provided with Microsoft “Roslyn” Community Technology Preview was named 'rcsi.exe'
references:
    - https://attack.mitre.org/techniques/T1218/
    - https://attack.mitre.org/techniques/T1072/
    - https://lolbas-project.github.io/lolbas/OtherMSBinaries/Csi/
    - https://lolbas-project.github.io/lolbas/OtherMSBinaries/Rcsi/
    - https://enigma0x3.net/2016/11/21/bypassing-application-whitelisting-by-using-rcsi-exe/
    - https://twitter.com/Z3Jpa29z/status/1317545798981324801
author: Huntrule Team
date: 2026-06-30
tags:
    - attack.lateral-movement
    - attack.execution
    - attack.stealth
    - attack.t1072
    - attack.t1218
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith:
              - '\csi.exe'
              - '\rcsi.exe'
        - OriginalFileName:
              - 'csi.exe'
              - 'rcsi.exe'
    selection_cli:
        Company: 'Microsoft Corporation'
    condition: all of selection*
falsepositives:
    - Unknown
level: medium