splunk-security_content/docs/_posts/2021-06-07-excessive_number_of_taskhost_processes.md

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title	excerpt	categories	last_modified_at	toc	toc_label	tags
Excessive number of taskhost processes	System Owner/User Discovery	Endpoint	2021-06-07	true		System Owner/User Discovery Discovery Splunk Enterprise Splunk Enterprise Security Splunk Cloud Endpoint

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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

Search

| 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

• Meterpreter

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

• https://attack.mitre.org/software/S0250/

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

• https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1059/meterpreter/taskhost_processes/logExcessiveTaskHost.log

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