name: Any Powershell DownloadString
id: 4d015ef2-7adf-11eb-95da-acde48001122
version: 3
date: '2022-04-07'
author: Michael Haag, Splunk
type: TTP
datamodel:
- Endpoint
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.
search: '| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time)
  as lastTime from datamodel=Endpoint.Processes where `process_powershell` Processes.process=*.DownloadString*  by
  Processes.dest Processes.user Processes.parent_process Processes.process_name Processes.original_file_name
  Processes.process Processes.process_id Processes.parent_process_id | `drop_dm_object_name(Processes)`
  | `security_content_ctime(firstTime)`| `security_content_ctime(lastTime)`| `any_powershell_downloadstring_filter`'
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
  confidence: 70
  context:
  - Source:Endpoint
  - Stage:Execution
  dataset:
  - https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1059.001/atomic_red_team/windows-sysmon.log
  impact: 80
  kill_chain_phases:
  - Exploitation
  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
  required_fields:
  - _time
  - Processes.dest
  - Processes.user
  - Processes.parent_process_name
  - Processes.parent_process
  - Processes.original_file_name
  - Processes.process_name
  - Processes.process
  - Processes.process_id
  - Processes.parent_process_path
  - Processes.process_path
  - Processes.parent_process_id
  risk_score: 56
  security_domain: endpoint
  supported_tas:
  - Splunk_TA_microsoft_sysmon
  asset_type: Endpoint