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Description

The following analytic detects the use of certutil.exe to download files using the -VerifyCtl and -split arguments. This behavior is identified by monitoring command-line executions for these specific arguments via Endpoint Detection and Response (EDR) telemetry. This activity is significant because certutil.exe is a legitimate tool often abused by attackers to download and execute malicious payloads. If confirmed malicious, this could allow an attacker to download and execute arbitrary files, potentially leading to code execution, data exfiltration, or further compromise of the system.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2024-08-15
  • Author: Michael Haag, Splunk
  • ID: 801ad9e4-8bfb-11eb-8b31-acde48001122

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1105 Ingress Tool Transfer Command And Control
Kill Chain Phase
  • Command and Control
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


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| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where `process_certutil` (Processes.process=*verifyctl* Processes.process=*split*) OR Processes.process=*verifyctl* by Processes.dest Processes.user Processes.original_file_name Processes.parent_process Processes.parent_process_name Processes.process_name Processes.process Processes.process_id Processes.parent_process_id 
| `drop_dm_object_name(Processes)` 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `certutil_download_with_verifyctl_and_split_arguments_filter`

Macros

The SPL above uses the following Macros:

:information_source: certutil_download_with_verifyctl_and_split_arguments_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

The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the Processes node of the Endpoint data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.

Known False Positives

Limited false positives in most environments, however tune as needed based on parent-child relationship or network connection.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
90.0 90 100 An instance of $parent_process_name$ spawning $process_name$ was identified on endpoint $dest$ by user $user$ attempting to download a file.

: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

source | version: 5