splunk-security_content/docs/_posts/2021-04-23-write_executable_in_smb_share.md

title, excerpt, categories, last_modified_at, toc, tags

title	excerpt	categories	last_modified_at	toc	tags
Write Executable in SMB Share	SMB/Windows Admin Shares	Endpoint	2021-04-23	true	TTP T1021.002 SMB/Windows Admin Shares Lateral Movement Splunk Enterprise Splunk Enterprise Security Splunk Cloud Endpoint Lateral Movement

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Description

This search is to detect suspicious dropping or creating an executable file in known sensitive SMB share. This technique is commonly used for lateral movement like how trickbot try to infect other machine in the infected network. This detection catch the access event (FILE WRITE) access to a share.

• Type: TTP
• Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
• Datamodel: Endpoint
• Last Updated: 2021-04-23
• Author: Teoderick Contreras, Splunk
• ID: f63c34fe-a435-11eb-935a-acde48001122

ATT&CK

ID	Technique	Tactic
T1021.002	SMB/Windows Admin Shares	Lateral Movement

Search

`wineventlog_security` EventCode=5145 Relative_Target_Name IN ("*.exe","*.dll") Object_Type=File Share_Name IN ("\\\\*\\C$","\\\\*\\IPC$","\\\\*\\admin$") Access_Mask= "0x2" 
| stats min(_time) as firstTime max(_time) as lastTime count by EventCode Share_Name Relative_Target_Name Object_Type Access_Mask user src_port Source_Address 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `write_executable_in_smb_share_filter`

Associated Analytic Story

• Trickbot

How To Implement

To successfully implement this search, you need to be ingesting Windows Security Event Logs with 5145 EventCode enabled. The Windows TA is also required. Also enable the object Audit access success/failure in your group policy.

Required field

• _time
• EventCode
• Share_Name
• Relative_Target_Name
• Object_Type
• Access_Mask
• user
• src_port
• Source_Address

Kill Chain Phase

• Lateral Movement

Known False Positives

unknown

RBA

Risk Score	Impact	Confidence	Message
70.0	70	100	user dropped or created an executable file in known sensitive SMB share. Share name=Share_Name, Target name=Relative_Target_Name, and Access mask=Access_Mask

Reference

• https://labs.vipre.com/trickbot-and-its-modules/
• https://blog.whitehat.eu/2019/05/incident-trickbot-ryuk-2.html

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/malware/trickbot/exe_smbshare/windows-security.log

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