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detections/endpoint/malicious_inprocserver32_modification.yml

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+name: Malicious InProcServer32 Modification
+id: 127c8d08-25ff-11ec-9223-acde48001122
+version: 1
+date: '2021-10-05'
+author: Michael Haag, Splunk
+type: TTP
+datamodel:
+- Endpoint
+description: The following analytic identifies a process modifying the registry with
+  a known malicious CLSID under InProcServer32. Most COM classes are registered with
+  the operating system and are identified by a GUID that represents the Class Identifier
+  (CLSID) within the registry (usually under HKLM\\Software\\Classes\\CLSID or HKCU\\Software\\Classes\\CLSID).  Behind
+  the implementation of a COM class is the server (some binary) that is referenced
+  within registry keys under the CLSID.  The LocalServer32 key represents a path to
+  an executable (exe) implementation, and the InprocServer32 key represents a path
+  to a dynamic link library (DLL) implementation (Bohops). During triage, review parallel
+  processes for suspicious activity. Pivot on the process GUID to see the full timeline
+  of events. Analyze the value and look for file modifications. Being this is looking
+  for inprocserver32, a DLL found in the value will most likely be loaded by a parallel
+  process.
+search: '| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Processes
+  by _time Processes.process_id Processes.process_name Processes.dest Processes.process_guid
+  Processes.user | `drop_dm_object_name(Processes)` | join process_guid [| tstats
+  `security_content_summariesonly` count FROM datamodel=Endpoint.Registry where Registry.registry_path=
+  "*\\CLSID\\{89565275-A714-4a43-912E-978B935EDCCC}\\InProcServer32\\(Default)" by
+  Registry.registry_path Registry.registry_key_name Registry.registry_value_name Registry.dest
+  Registry.process_guid Registry.user | `drop_dm_object_name(Registry)` | fields _time
+  dest registry_path registry_key_name registry_value_name process_name process_path
+  process process_guid user] | stats count min(_time) as firstTime max(_time) as lastTime
+  by dest, process_name registry_path registry_key_name registry_value_name user |
+  `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `malicious_inprocserver32_modification_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 `Registry` 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 should be limited, filter as needed. In our
+  test case, Remcos used regsvr32.exe to modify the registry. It may be required,
+  dependent upon the EDR tool producing registry events, to remove (Default) from
+  the command-line.
+references:
+- https://bohops.com/2018/06/28/abusing-com-registry-structure-clsid-localserver32-inprocserver32/
+- https://tria.ge/210929-ap75vsddan
+- https://www.virustotal.com/gui/file/cb77b93150cb0f7fe65ce8a7e2a5781e727419451355a7736db84109fa215a89
+tags:
+  analytic_story:
+  - Suspicious Regsvr32 Activity
+  - Remcos
+  dataset:
+  - https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/malware/remcos/remcos/windows-sysmon.log
+  kill_chain_phases:
+  - Exploitation
+  mitre_attack_id:
+  - T1218.010
+  - T1112
+  product:
+  - Splunk Enterprise
+  - Splunk Enterprise Security
+  - Splunk Cloud
+  required_fields:
+  - _time
+  - dest
+  - process_name
+  - registry_path
+  - registry_key_name
+  - registry_value_name
+  - user
+  security_domain: endpoint
+  impact: 80
+  confidence: 100
+  risk_score: 80
+  context:
+  - Source:Endpoint
+  - Stage:Defense Evasion
+  message: The $process_name$ was identified on endpoint $dest$ modifying the registry
+    with a known malicious clsid under InProcServer32.
+  observable:
+  - name: dest
+    type: Hostname
+    role:
+    - Victim
+  - name: process_name
+    type: Process
+    role:
+    - Child Process
+  automated_detection_testing: passed

detections/endpoint/process_writing_dynamicwrapperx.yml

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+name: Process Writing DynamicWrapperX
+id: b0a078e4-2601-11ec-9aec-acde48001122
+version: 1
+date: '2021-10-05'
+author: Michael Haag, Splunk
+type: Hunting
+datamodel:
+- Endpoint
+description: DynamicWrapperX is an ActiveX component that can be used in a script
+  to call Windows API functions, but it requires the dynwrapx.dll to be installed
+  and registered. With that, a binary writing dynwrapx.dll to disk and registering
+  it into the registry is highly suspect. Why is it needed? In most malicious instances,
+  it will be written to disk at a non-standard location. During triage, review parallel
+  processes and pivot on the process_guid. Review the registry for any suspicious
+  modifications meant to load dynwrapx.dll. Identify any suspicious module loads of
+  dynwrapx.dll. This will identify the process that will invoke vbs/wscript/cscript.
+search: '| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Processes
+  by _time Processes.process_id Processes.process_name Processes.dest Processes.process_guid
+  Processes.user | `drop_dm_object_name(Processes)` | join process_guid [| tstats
+  `security_content_summariesonly` count FROM datamodel=Endpoint.Filesystem where
+  Filesystem.file_name="dynwrapx.dll" by _time Filesystem.dest Filesystem.file_create_time
+  Filesystem.file_name Filesystem.file_path Filesystem.process_guid Filesystem.user
+  | `drop_dm_object_name(Filesystem)` | fields _time process_guid file_path file_name
+  file_create_time user dest process_name] | stats count min(_time) as firstTime max(_time)
+  as lastTime by dest process_name process_guid file_name file_path file_create_time
+  user | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`
+  | `process_writing_dynamicwrapperx_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 `Filesystem`
+  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 should be limited, however it is possible to
+  filter by Processes.process_name and specific processes (ex. wscript.exe). Filter
+  as needed. This may need modification based on EDR telemetry and how it brings in registry data. For example, removal of (Default).
+references:
+- https://blog.f-secure.com/hunting-for-koadic-a-com-based-rootkit/
+- https://www.script-coding.com/dynwrapx_eng.html
+- https://bohops.com/2018/06/28/abusing-com-registry-structure-clsid-localserver32-inprocserver32/
+- https://tria.ge/210929-ap75vsddan
+- https://www.virustotal.com/gui/file/cb77b93150cb0f7fe65ce8a7e2a5781e727419451355a7736db84109fa215a89
+tags:
+  analytic_story:
+  - Remcos
+  dataset:
+  - https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/malware/remcos/remcos/windows-sysmon.log
+  kill_chain_phases:
+  - Exploitation
+  mitre_attack_id:
+  - T1059
+  - T1559.001
+  product:
+  - Splunk Enterprise
+  - Splunk Enterprise Security
+  - Splunk Cloud
+  required_fields:
+  - _time
+  - dest
+  - process_name
+  - process_guid
+  - file_name
+  - file_path
+  - file_create_time user
+  security_domain: endpoint
+  impact: 80
+  confidence: 100
+  risk_score: 80
+  context:
+  - Source:Endpoint
+  - Stage:Defense Evasion
+  message: An instance of $process_name$ was identified on endpoint $dest$ downloading
+    the DynamicWrapperX dll.
+  observable:
+  - name: user
+    type: User
+    role:
+    - Victim
+  - name: dest
+    type: Hostname
+    role:
+    - Victim
+  - name: process_name
+    type: Process
+    role:
+    - Child Process
+  automated_detection_testing: passed

detections/endpoint/winhlp32_spawning_a_process.yml

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+name: Winhlp32 Spawning a Process
+id: d17dae9e-2618-11ec-b9f5-acde48001122
+version: 1
+date: '2021-10-05'
+author: Michael Haag, Splunk
+type: TTP
+datamodel:
+- Endpoint
+description: The following analytic identifies winhlp32.exe, found natively in `c:\windows\`,
+  spawning a child process that loads a file out of appdata, programdata, or temp.
+  Winhlp32.exe has a rocky past in that multiple vulnerabilities were found and added
+  to MetaSploit. WinHlp32.exe is required to display 32-bit Help files that have the
+  ".hlp" file name extension. This particular instance is related to a Remcos sample
+  where dynwrapx.dll is added to the registry under inprocserver32, and later module
+  loaded by winhlp32.exe to spawn wscript.exe and load a vbs or file from disk. During
+  triage, review parallel processes to identify further suspicious behavior. Review
+  module loads for unsuspecting unsigned modules. Capture any file modifications and
+  analyze.
+search: '| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time)
+  as lastTime from datamodel=Endpoint.Processes where Processes.parent_process_name=winhlp32.exe
+  Processes.process IN ("*\\appdata\\*","*\\programdata\\*", "*\\temp\\*") by Processes.dest
+  Processes.user Processes.parent_process_name 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)` | `winhlp32_spawning_a_process_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 should be limited as winhlp32.exe is typically
+  not used with the latest flavors of Windows OS. However, filter as needed.
+references:
+- https://www.exploit-db.com/exploits/16541
+- https://tria.ge/210929-ap75vsddan
+- https://www.virustotal.com/gui/file/cb77b93150cb0f7fe65ce8a7e2a5781e727419451355a7736db84109fa215a89
+tags:
+  analytic_story:
+  - Remcos
+  dataset:
+  - https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/malware/remcos/remcos/windows-sysmon.log
+  kill_chain_phases:
+  - Exploitation
+  mitre_attack_id:
+  - T1055
+  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
+  security_domain: endpoint
+  impact: 80
+  confidence: 100
+  risk_score: 80
+  context:
+  - Source:Endpoint
+  - Stage:Defense Evasion
+  message: An instance of $parent_process_name$ spawning $process_name$ was identified
+    on endpoint $dest$, and is not typical activity for this process.
+  observable:
+  - name: user
+    type: User
+    role:
+    - Victim
+  - name: dest
+    type: Hostname
+    role:
+    - Victim
+  - name: parent_process_name
+    type: Parent Process
+    role:
+    - Parent Process
+  - name: process_name
+    type: Process
+    role:
+    - Child Process
+  automated_detection_testing: passed

tests/endpoint/malicious_inprocserver32_modification.test.yml

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+name: Malicious InProcServer32 Modification Unit Test
+tests:
+- name: Malicious InProcServer32 Modification
+  file: endpoint/malicious_inprocserver32_modification.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/malware/remcos/remcos/windows-sysmon.log
+    source:  XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
+    sourcetype: xmlwineventlog

tests/endpoint/process_writing_dynamicwrapperx.test.yml

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+name: Process Writing DynamicWrapperX Unit Test
+tests:
+- name: Process Writing DynamicWrapperX
+  file: endpoint/process_writing_dynamicwrapperx.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/malware/remcos/remcos/windows-sysmon.log
+    source:  XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
+    sourcetype: xmlwineventlog

tests/endpoint/winhlp32_spawning_a_process.test.yml

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+name: Winhlp32 Spawning a Process Unit Test
+tests:
+- name: Winhlp32 Spawning a Process
+  file: endpoint/winhlp32_spawning_a_process.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/malware/remcos/remcos/windows-sysmon.log
+    source:  XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
+    sourcetype: xmlwineventlog