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Description

The following analytic identifies Regsvr32.exe utilizing the silent switch to load DLLs. This technique has most recently been seen in IcedID campaigns to load its initial dll that will download the 2nd stage loader that will download and decrypt the config payload. The switch type may be either a hyphen - or forward slash /. This behavior is typically found with -s, and it is possible there are more switch types that may be used. \ During triage, review parallel processes and capture any artifacts that may have landed on disk. Isolate and contain the endpoint as necessary.

  • Type: Anomaly
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2021-07-27
  • Author: Teoderick Contreras, Splunk
  • ID: c9ef7dc4-eeaf-11eb-b2b6-acde48001122

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1218 System Binary Proxy Execution Defense Evasion
T1218.010 Regsvr32 Defense Evasion
Kill Chain Phase
  • Exploitation
NIST
  • DE.AE
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_regsvr32` by Processes.user Processes.process_name Processes.process Processes.parent_process_name Processes.original_file_name Processes.dest Processes.process_id 
| `drop_dm_object_name(Processes)` 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| where match(process,"(?i)[\-
|\/][Ss]{1}") 
| `regsvr32_with_known_silent_switch_cmdline_filter`

Macros

The SPL above uses the following Macros:

:information_source: regsvr32_with_known_silent_switch_cmdline_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 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

minimal. but network operator can use this application to load dll.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
56.0 70 80 An instance of $parent_process_name$ spawning $process_name$ was identified on endpoint $dest$ by user $user$ attempting to load a DLL using the silent parameter.

: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: 2