mirror of
https://github.com/splunk/security_content
synced 2026-06-08 17:32:49 +00:00
Bhavin Patel
76 lines
3.1 KiB
YAML
76 lines
3.1 KiB
YAML
name: Windows Powershell DownloadString
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id: 04d76f1c-af1e-4732-a365-24a4e59d6e73
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version: 1
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date: '2024-03-19'
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author: Michael Haag, Splunk
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status: validation
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type: TTP
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description: The following analytic identifies the use of PowerShell downloading a
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file using `DownloadString` method. This particular method is utilized in many different
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PowerShell frameworks to download files and output to disk. Identify the source
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(IP/domain) and destination file and triage appropriately. If AMSI logging or PowerShell
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transaction logs are available, review for further details of the implant.
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data_source:
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- Windows Security 4688
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search:
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selection1:
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process.file.name:
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- powershell_ise.exe
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- powershell.exe
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- sqltoolsps.exe
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- sqlps.exe
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- pwsh.exe
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- pwsh.exe
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selection2:
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process.cmd_line|re: DownloadString
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condition: selection1 and selection2
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how_to_implement: The detection is based on data that originates from Endpoint Detection
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and Response (EDR) agents. These agents are designed to provide security-related
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telemetry from the endpoints where the agent is installed. To implement this search,
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you must ingest logs that contain the process GUID, process name, and parent process.
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Additionally, you must ingest complete command-line executions. These logs must
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be processed using the appropriate Splunk Technology Add-ons that are specific to
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the EDR product. The logs must also be mapped to the `Processes` node of the `Endpoint`
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data model. Use the Splunk Common Information Model (CIM) to normalize the field
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names and speed up the data modeling process.
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known_false_positives: False positives may be present and filtering will need to occur
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by parent process or command line argument. It may be required to modify this query
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to an EDR product for more granular coverage.
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references:
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- https://docs.microsoft.com/en-us/dotnet/api/system.net.webclient.downloadstring?view=net-5.0
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- https://blog.malwarebytes.com/malwarebytes-news/2021/02/lazyscripter-from-empire-to-double-rat/
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- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1059.001/T1059.001.md
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- https://thedfirreport.com/2023/05/22/icedid-macro-ends-in-nokoyawa-ransomware/
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tags:
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analytic_story:
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- Winter Vivern
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- Ingress Tool Transfer
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- Hermetic Wiper
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- Malicious PowerShell
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- HAFNIUM Group
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- Data Destruction
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- IcedID
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- SysAid On-Prem Software CVE-2023-47246 Vulnerability
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asset_type: Endpoint
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confidence: 70
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impact: 80
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message: An instance of $parent_process_name$ spawning $process_name$ was identified
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on endpoint $dest$ by user $user$. This behavior identifies the use of DownloadString
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within PowerShell.
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mitre_attack_id:
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- T1059
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- T1059.001
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- T1105
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observable: []
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product:
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- Splunk Behavioral Analytics
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required_fields: []
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risk_score: 56
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security_domain: endpoint
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tests:
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- name: True Positive Test
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attack_data:
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- data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1059.001/atomic_red_team/windows-security-2.log
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source: XmlWinEventLog:Security
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sourcetype: XmlWinEventLog
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