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Description

The following analytic identifies DCRat "forkbomb" payload feature. This technique was seen in dark crystal RAT backdoor capabilities where it will execute several cmd child process executing "notepad.exe & pause". This analytic detects the multiple cmd.exe and child process notepad.exe execution using batch script in the targeted host within 30s timeframe. this TTP can be a good pivot to check DCRat infection.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2022-07-28
  • Author: Teoderick Contreras, Splunk
  • ID: 2bb1a362-7aa8-444a-92ed-1987e8da83e1

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1059.003 Windows Command Shell Execution
T1059 Command and Scripting Interpreter Execution
Kill Chain Phase
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 3
  • CIS 5
  • CIS 16
CVE
1
2
3
4
5
6
7
| tstats `security_content_summariesonly` values(Processes.process) as process values(Processes.parent_process) as parent_process values(Processes.parent_process_id) as parent_process_id values(Processes.process_id) as process_id dc(Processes.parent_process_id) as parent_process_id_count dc(Processes.process_id) as process_id_count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.parent_process_name= "cmd.exe" (Processes.process_name = "notepad.exe" OR Processes.original_file_name= "notepad.exe") Processes.parent_process = "*.bat*" by  Processes.parent_process_name Processes.process_name Processes.original_file_name Processes.parent_process Processes.dest Processes.user  _time span=30s 
| where parent_process_id_count>= 10 AND process_id_count >=10 
| `drop_dm_object_name(Processes)` 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `windows_command_shell_dcrat_forkbomb_payload_filter`

Macros

The SPL above uses the following Macros:

:information_source: windows_command_shell_dcrat_forkbomb_payload_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _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

How To Implement

To successfully implement this search, you need to be ingesting logs with the process name, parent process, and command-line executions from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA. Tune and filter known instances of wermgr.exe may be used.

Known False Positives

unknown

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
81.0 90 90 Multiple cmd.exe processes with child process of notepad.exe executed on $dest$

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

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