splunk-security_content/docs/_posts/2021-03-01-any_powershell_downloadfile.md

title, excerpt, categories, last_modified_at, toc, toc_label, tags

title	excerpt	categories	last_modified_at	toc	toc_label	tags
Any Powershell DownloadFile	Command and Scripting Interpreter, PowerShell	Endpoint	2021-03-01	true		Command and Scripting Interpreter Execution PowerShell Execution Splunk Enterprise Splunk Enterprise Security Splunk Cloud CVE-2021-44228 Endpoint

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Description

The following analytic identifies the use of PowerShell downloading a file using DownloadFile method. This particular method is utilized in many different PowerShell frameworks to download files and output to disk. Identify the source (IP/domain) and destination file and triage appropriately. If AMSI logging or PowerShell transaction logs are available, review for further details of the implant.

• Type: TTP
• Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
• Datamodel: Endpoint
• Last Updated: 2021-03-01
• Author: Michael Haag, Splunk
• ID: 1a93b7ea-7af7-11eb-adb5-acde48001122

ATT&CK

ID	Technique	Tactic
T1059	Command and Scripting Interpreter	Execution

| T1059.001 | PowerShell | Execution |

Search

| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where `process_powershell` Processes.process=*DownloadFile* by Processes.dest Processes.user Processes.parent_process Processes.process_name Processes.original_file_name Processes.process Processes.process_id Processes.parent_process_id 
| `drop_dm_object_name(Processes)` 
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| `any_powershell_downloadfile_filter`

Associated Analytic Story

• Malicious PowerShell
• Ingress Tool Transfer
• Log4Shell CVE-2021-44228

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.

Required field

• _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

Kill Chain Phase

• Exploitation

Known False Positives

False positives may be present and filtering will need to occur by parent process or command line argument. It may be required to modify this query to an EDR product for more granular coverage.

RBA

Risk Score	Impact	Confidence	Message
56.0	80	70	An instance of parent_process_name spawning process_name was identified on endpoint dest by user user. This behavior identifies the use of DownloadFile within PowerShell.

CVE

ID	Summary	CVSS
CVE-2021-44228	Apache Log4j2 2.0-beta9 through 2.12.1 and 2.13.0 through 2.15.0 JNDI features used in configuration, log messages, and parameters do not protect against attacker controlled LDAP and other JNDI related endpoints. An attacker who can control log messages or log message parameters can execute arbitrary code loaded from LDAP servers when message lookup substitution is enabled. From log4j 2.15.0, this behavior has been disabled by default. From version 2.16.0, this functionality has been completely removed. Note that this vulnerability is specific to log4j-core and does not affect log4net, log4cxx, or other Apache Logging Services projects.	9.3

Reference

• https://docs.microsoft.com/en-us/dotnet/api/system.net.webclient.downloadfile?view=net-5.0
• https://blog.malwarebytes.com/malwarebytes-news/2021/02/lazyscripter-from-empire-to-double-rat/
• https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1059.001/T1059.001.md

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/T1059.001/atomic_red_team/windows-sysmon.log

source | version: 2