Windows Process Creation: Suspicious Microsoft Csi.exe or Rcsi.exe with C# Execution Capability

Alerts on Windows executions of Microsoft’s csi.exe/rcsi.exe that can be used to run C# code from command-line.

FreeReviewedSigma · Medium · v2

Product: windows
Category: process_creation
Author: Konstantin Grishchenko, oscd.community (SigmaHQ), DRL 1.1
Published: 2020-10-17
Updated: 2026-07-31

ATT&CK techniques

Execution → Lateral Movement

Recon
Resource Dev
Initial Access
Execution
- T1072Software Deployment Tools
Persistence
Priv Esc
Defense Evasion
- T1218System Binary Proxy Execution
Cred Access
Discovery
Lateral Movement
- T1072Software Deployment Tools
Collection
C2
Exfiltration
Impact

What it detects

This rule flags process creation events where Image ends with either csi.exe or rcsi.exe and the OriginalFileName matches the same binary names. The behavior matters because these Microsoft-signed utilities can execute C# code from a file via command-line parameters, which may be abused for stealthy execution. Telemetry required is Windows process creation data including Image path and OriginalFileName, plus process metadata indicating the Company is Microsoft Corporation.

Reporting behind it

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Windows Process Creation: Suspicious Microsoft Csi.exe or Rcsi.exe with C# Execution Capability

Pivot detection · T1218 · 9 related

Changelog

v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

suspicious-microsoft-csi-exe-or-rcsi-exe-execution-on-windows-40b95d31

title: "Windows Process Creation: Suspicious Microsoft Csi.exe or Rcsi.exe with C# Execution Capability"
id: 035d224c-aa8a-4e94-9979-05bc111b60f7
status: test
description: This rule flags process creation events where Image ends with either csi.exe or rcsi.exe and the OriginalFileName matches the same binary names. The behavior matters because these Microsoft-signed utilities can execute C# code from a file via command-line parameters, which may be abused for stealthy execution. Telemetry required is Windows process creation data including Image path and OriginalFileName, plus process metadata indicating the Company is Microsoft Corporation.
references:
  - 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
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_csi_execution.yml
author: Konstantin Grishchenko, oscd.community, Huntrule Team
date: 2020-10-17
modified: 2022-07-11
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:
  - Legitimate usage by software developers
level: medium
license: DRL-1.1
related:
  - id: 40b95d31-1afc-469e-8d34-9a3a667d058e
    type: derived

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