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Description

The following analytic identifies DLLHost.exe with no command line arguments with a network connection. It is unusual for DLLHost.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. DLLHost.exe is natively found in C:\Windows\system32 and C:\Windows\syswow64.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2021-10-13
  • Author: Michael Haag, Splunk
  • ID: f1c07594-a141-11eb-8407-acde48001122

ATT&CK

ID Technique Tactic
T1055 Process Injection Defense Evasion, Privilege Escalation 

| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Processes where Processes.process_name=dllhost.exe by _time span=1h  Processes.process_guid 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="(dllhost\.exe.{0,4}$)" 
| join  process_guid [
| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Ports where Ports.dest_port !="0" by Ports.process_guid 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 process_guid connection_to_CNC dest_port 
| `dllhost_with_no_command_line_arguments_with_network_filter`

Associated Analytic Story

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.

Required field

  • _time
  • EventID
  • process_name
  • process_id
  • parent_process_name
  • dest_port
  • process_path

Kill Chain Phase

  • Exploitation

Known False Positives

Although unlikely, some legitimate third party applications may use a moved copy of dllhost, triggering a false positive.

RBA

Risk Score Impact Confidence Message
49.0 70 70 The process $process_name$ was spawned by $parent_image$ without any command-line arguments on $dest$ by $user$.

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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