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Description

This detection targets behaviors observed in post exploit kits like Meterpreter and Koadic that are run in memory. We have observed that these tools must invoke an excessive number of taskhost.exe and taskhostex.exe processes to complete various actions (discovery, lateral movement, etc.). It is extremely uncommon in the course of normal operations to see so many distinct taskhost and taskhostex processes running concurrently in a short time frame.

  • Type: Anomaly
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2021-06-07
  • Author: Michael Hart
  • ID: f443dac2-c7cf-11eb-ab51-acde48001122

ATT&CK

ID Technique Tactic
T1033 System Owner/User Discovery Discovery

| tstats `security_content_summariesonly` values(Processes.process_id) as process_ids  min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Processes WHERE Processes.process_name = "taskhost.exe" OR Processes.process_name = "taskhostex.exe" BY Processes.dest Processes.process_name _time span=1h 
| `drop_dm_object_name(Processes)` 
| eval pid_count=mvcount(process_ids) 
| eval taskhost_count_=if(process_name == "taskhost.exe", pid_count, 0) 
| eval taskhostex_count_=if(process_name == "taskhostex.exe", pid_count, 0) 
| stats sum(taskhost_count_) as taskhost_count, sum(taskhostex_count_) as taskhostex_count by _time, dest, firstTime, lastTime 
| where taskhost_count > 10 and taskhostex_count > 10 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `excessive_number_of_taskhost_processes_filter`

Associated Analytic Story

How To Implement

To successfully implement this search you need to be ingesting events related to processes on the endpoints that include the name of the process and process id into the Endpoint datamodel in the Processes node.

Required field

  • _time
  • Processes.process_id
  • Processes.process_name
  • Processes.dest
  • Processes.user

Kill Chain Phase

  • Exploitation

Known False Positives

Administrators, administrative actions or certain applications may run many instances of taskhost and taskhostex concurrently. Filter as needed.

RBA

Risk Score Impact Confidence Message
56.0 80 70 An excessive amount of $process_name$ was executed on $dest$ indicative of suspicious behavior.

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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