name: Any Powershell DownloadString
id: 4d015ef2-7adf-11eb-95da-acde48001122
version: 3
date: '2022-04-07'
author: Michael Haag, Splunk
status: production
type: TTP
description: The following analytic identifies the use of PowerShell downloading a
  file using `DownloadString` method. This particular method is utilized in many different
  PowerShell frameworks to download files and output to disk. Identify the source
  (IP/domain) and destination file and triage appropriately. If AMSI logging or PowerShell
  transaction logs are available, review for further details of the implant.
data_source:
- Sysmon Event ID 1
search:
  selection1:
    OriginalFileName: pwsh.dll
  selection2:
    Image|endswith:
    - pwsh.exe
    - sqlps.exe
    - sqltoolsps.exe
    - powershell.exe
    - powershell_ise.exe
  selection3:
    OriginalFileName: PowerShell.EXE
  selection4:
    OriginalFileName: powershell_ise.EXE
  selection5:
    CommandLine: '*.DownloadString*'
  condition: (selection1 or selection2 or selection3 or selection4) and selection5
how_to_implement: To successfully implement this search you need to be ingesting information
  on process that include the name of the process responsible for the changes from
  your endpoints into the `Endpoint` datamodel in the `Processes` node. In addition,
  confirm the latest CIM App 4.20 or higher is installed and the latest TA for the
  endpoint product.
known_false_positives: False positives may be present and filtering will need to occur
  by parent process or command line argument. It may be required to modify this query
  to an EDR product for more granular coverage.
references:
- https://docs.microsoft.com/en-us/dotnet/api/system.net.webclient.downloadstring?view=net-5.0
- https://blog.malwarebytes.com/malwarebytes-news/2021/02/lazyscripter-from-empire-to-double-rat/
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1059.001/T1059.001.md
tags:
  analytic_story:
  - Hermetic Wiper
  - Malicious PowerShell
  - HAFNIUM Group
  - Ingress Tool Transfer
  asset_type: Endpoint
  confidence: 70
  impact: 80
  message: An instance of $parent_process_name$ spawning $process_name$ was identified
    on endpoint $dest$ by user $user$. This behavior identifies the use of DownloadString
    within PowerShell.
  mitre_attack_id:
  - T1059
  - T1059.001
  - T1105
  observable:
  - name: user
    type: User
    role:
    - Victim
  - name: dest
    type: Hostname
    role:
    - Victim
  - name: parent_process_name
    type: Process
    role:
    - Parent Process
  - name: process_name
    type: Process
    role:
    - Child Process
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  risk_score: 56
  security_domain: endpoint
tests:
- name: True Positive Test
  attack_data:
  - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1059.001/atomic_red_team/windows-sysmon.log
    source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
    sourcetype: xmlwineventlog