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P4T12ICK
96 lines
3.9 KiB
YAML
96 lines
3.9 KiB
YAML
name: Windows Powershell DownloadFile
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id: 46440222-81d5-44b1-a376-19dcd70d1b08
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version: 1
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date: '2022-02-11'
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author: Jose Hernandez, Michael Haag, Splunk
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type: Anomaly
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datamodel:
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- Endpoint_Processes
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description: The following analytic identifies the use of PowerShell downloading a
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file using `DownloadFile` 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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search: '| from read_ssa_enriched_events() | eval timestamp=parse_long(ucast(map_get(input_event,
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"_time"), "string", null)), cmd_line=lower(ucast(map_get(input_event, "process"),
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"string", null)), process_name=lower(ucast(map_get(input_event, "process_name"),
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"string", null)), process_path=ucast(map_get(input_event, "process_path"), "string",
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null), parent_process_name=ucast(map_get(input_event, "parent_process_name"), "string",
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null), event_id=ucast(map_get(input_event, "event_id"), "string", null) | where
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cmd_line IS NOT NULL AND process_name IS NOT NULL | where process_name="pwsh.exe"
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OR process_name="pwsh.exe" OR process_name="sqlps.exe" OR process_name="sqltoolsps.exe"
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OR process_name="powershell.exe" OR process_name="powershell_ise.exe" | where (like
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(cmd_line, "%downloadfile%")) | eval start_time=timestamp, end_time=timestamp, entities=mvappend(ucast(map_get(input_event,
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"dest_user_id"), "string", null), ucast(map_get(input_event, "dest_device_id"),
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"string", null)), body=create_map(["event_id", event_id, "cmd_line", cmd_line, "process_name",
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process_name, "parent_process_name", parent_process_name, "process_path", process_path])
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| into write_ssa_detected_events();'
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how_to_implement: To successfully implement this search you need to be ingesting information
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on process that include the name of the process responsible for the changes from
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your endpoints into the `Endpoint` datamodel in the `Processes` node. In addition,
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confirm the latest CIM App 4.20 or higher is installed and the latest TA for the
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endpoint product.
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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.downloadfile?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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tags:
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analytic_story:
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- Malicious PowerShell
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- Ingress Tool Transfer
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- Log4Shell CVE-2021-44228
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cis20:
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- CIS 8
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confidence: 70
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context:
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- Source:Endpoint
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- Stage:Lateral Movement
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dataset:
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- https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1059.001/atomic_red_team/downloadfile_windows-security.log
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impact: 50
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kill_chain_phases:
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- Exploitation
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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 DownloadFile
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within PowerShell.
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mitre_attack_id:
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- T1020
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nist:
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- PR.PT
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- DE.CM
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observable:
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- name: dest_user_id
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type: User
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role:
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- Victim
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- name: dest_device_id
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type: Hostname
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role:
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- Victim
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- name: parent_process_name
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type: Process
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role:
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- Parent Process
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- name: process_name
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type: Process
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role:
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- Child Process
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product:
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- Splunk Behavioral Analytics
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required_fields:
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- _time
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- dest_device_id
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- process_name
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- parent_process_name
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- process_path
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- dest_user_id
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- process
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- cmd_line
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risk_score: 35
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risk_severity: low
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security_domain: endpoint
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asset_type: Endpoint
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