title: Suspicious Csi.exe Usage
author: Konstantin Grishchenko, oscd.community
date: 2020/10/17
description: Csi.exe is a signed binary from Microsoft that comes with Visual Studio
  and provides C# interactive capabilities. It can be used 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'
detection:
  SELECTION_1:
    EventID: 1
  SELECTION_2:
    Image: '*\csi.exe'
  SELECTION_3:
    Image: '*\rcsi.exe'
  SELECTION_4:
    OriginalFileName: csi.exe
  SELECTION_5:
    OriginalFileName: rcsi.exe
  SELECTION_6:
    Company: Microsoft Corporation
  condition: (SELECTION_1 and (SELECTION_2 or SELECTION_3 or SELECTION_4 or SELECTION_5)
    and SELECTION_6)
falsepositives:
- Legitimate usage by software developers
fields:
- ComputerName
- User
- CommandLine
- ParentCommandLine
id: 40b95d31-1afc-469e-8d34-9a3a667d058e
level: medium
logsource:
  category: process_creation
  product: windows
modified: 2021/05/11
references:
- https://github.com/LOLBAS-Project/LOLBAS/blob/master/yml/OtherMSBinaries/Csi.yml
- https://github.com/LOLBAS-Project/LOLBAS/blob/master/yml/OtherMSBinaries/Rcsi.yml
- https://enigma0x3.net/2016/11/21/bypassing-application-whitelisting-by-using-rcsi-exe/
- https://twitter.com/Z3Jpa29z/status/1317545798981324801
status: experimental
tags:
- attack.execution
- attack.t1072
- attack.defense_evasion
- attack.t1218
ruletype: SIGMA