Windows: Suspicious Execution of CSharp Interactive Console via PowerShell

ATT&CK techniques

Execution → Defense Evasion

Recon
Resource Dev
Initial Access
Execution
- T1127Trusted Developer Utilities Proxy Execution
Persistence
Priv Esc
Defense Evasion
- T1127Trusted Developer Utilities Proxy Execution
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule identifies process creation where the C# interactive console (csi.exe) is launched by PowerShell-related parent processes. Attackers may use interactive .NET/C# tooling to rapidly execute code and evade traditional scripting or deployment paths. The detection relies on Windows process creation telemetry, matching the child executable name and the parent executable path endings (PowerShell/pwsh/Powershell ISE).

Reporting behind it

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Windows: Suspicious Execution of CSharp Interactive Console via PowerShell

Pivot detection · T1127 · 9 related

Changelog

v2

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.

powershell-executing-csharp-interactive-console-csi-exe-on-windows-a9e416a8

title: "Windows: Suspicious Execution of CSharp Interactive Console via PowerShell"
id: 9d284fe3-61e4-4fb1-ba86-916d8e369815
status: test
description: This rule identifies process creation where the C# interactive console (csi.exe) is launched by PowerShell-related parent processes. Attackers may use interactive .NET/C# tooling to rapidly execute code and evade traditional scripting or deployment paths. The detection relies on Windows process creation telemetry, matching the child executable name and the parent executable path endings (PowerShell/pwsh/Powershell ISE).
references:
  - https://redcanary.com/blog/detecting-attacks-leveraging-the-net-framework/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_csi_use_of_csharp_console.yml
author: Michael R. (@nahamike01), Huntrule Team
date: 2020-03-08
modified: 2022-07-14
tags:
  - attack.execution
  - attack.stealth
  - attack.t1127
logsource:
  category: process_creation
  product: windows
detection:
  selection:
    Image|endswith: \csi.exe
    ParentImage|endswith:
      - \powershell.exe
      - \pwsh.exe
      - \powershell_ise.exe
    OriginalFileName: csi.exe
  condition: selection
falsepositives:
  - Possible depending on environment. Pair with other factors such as net connections, command-line args, etc.
level: high
license: DRL-1.1
related:
  - id: a9e416a8-e613-4f8b-88b8-a7d1d1af2f61
    type: derived

Convert

This rule as a query you can run. Uses no unlock credit.

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