rundll32

detections/endpoint/rundll32_with_no_command_line_arguments_with_network.yml

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+name: Rundll32 with no Command Line Arguments with Network
+id: 35307032-a12d-11eb-835f-acde48001122
+version: 1
+date: '2021-04-19'
+author: Michael Haag, Splunk
+type: batch
+datamodel:
+- Endpoint
+description: The following analytic identifies rundll32.exe with no command line arguments and performing a network connection. 
+  It is unusual for rundll32.exe to execute with no command line arguments present.
+  This particular behavior is common with malicious software, including Cobalt Strike.
+  During investigation, triage any network connections and parallel processes. Identify
+  any suspicious module loads related to credential dumping or file writes. Rundll32.exe
+  is natively found in C:\Windows\system32 and C:\Windows\syswow64.
+search: '| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Processes
+  where Processes.process_name=rundll32.exe by _time span=1h  Processes.process_id Processes.process_name
+  Processes.dest Processes.process_path Processes.process Processes.parent_process_name 
+  | `drop_dm_object_name(Processes)` 
+  | `security_content_ctime(firstTime)` 
+  | `security_content_ctime(lastTime)` 
+  | regex process="(rundll32\.exe.{0,4}$)" 
+  | join  process_id 
+  [| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Ports where Ports.dest_port !="0" by Ports.process_id Ports.dest Ports.dest_port| `drop_dm_object_name(Ports)` | rename  dest as connection_to_CNC] 
+  | table _time dest  parent_process_name process_name process_path process_id connection_to_CNC dest_port 
+  | `rundll32_with_no_command_line_arguments_with_network_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` and `port` node.
+known_false_positives: Although unlikely, some legitimate applications may use a moved
+  copy of rundll32, triggering a false positive.
+references:
+  - https://attack.mitre.org/techniques/T1218/011/
+  - https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1218.011/T1218.011.md
+  - https://lolbas-project.github.io/lolbas/Binaries/Rundll32
+  - https://bohops.com/2018/02/26/leveraging-inf-sct-fetch-execute-techniques-for-bypass-evasion-persistence/
+tags:
+  analytic_story:
+  - Suspicious Rundll32 Activity
+  - Cobalt Strike
+  dataset: []
+  kill_chain_phases:
+  - Exploitation
+  mitre_attack_id:
+  - T1218.011
+  product:
+  - Splunk Enterprise
+  - Splunk Enterprise Security
+  - Splunk Cloud
+  required_fields:
+  - _time
+  - EventID
+  - process_name
+  - process_id
+  - parent_process_name
+  - dest_port
+  - process_path
+  security_domain: endpoint

tests/endpoint/rundll32_with_no_command_line_arguments_with_network.test.yml

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+name: Rundll32 with no Command Line Arguments with Network Unit Test
+tests:
+- name: Rundll32 with no Command Line Arguments with Network
+  file: endpoint/rundll32_with_no_command_line_arguments_with_network.yml
+  pass_condition: '| stats count | where count > 0'
+  earliest_time: '-24h'
+  latest_time: 'now'
+  attack_data:
+  - file_name: windows-sysmon.log
+    data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1218.011/atomic_red_team/windows-sysmon.log
+    source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
+    sourcetype: xmlwineventlog