The following analytic identifies executable files (.exe or .dll) being written to Windows administrative SMB shares (Admin$, IPC$, C$). This represents suspicious behavior as its commonly used by tools like like PsExec/PaExec and others to stage service binaries before creating and starting a Windows service on remote endpoints. Red Teams and adversaries alike may abuse administrative shares for lateral movement and remote code execution. The Trickbot malware family also implements this behavior to try to infect other machines in the infected network.
- Type: TTP
- Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Last Updated: 2021-11-18
- Author: Teoderick Contreras, Mauricio Velazco, Splunk
- ID: f63c34fe-a435-11eb-935a-acde48001122
|T1021||Remote Services||Lateral Movement|
|T1021.002||SMB/Windows Admin Shares||Lateral Movement|
`wineventlog_security` EventCode=5145 Relative_Target_Name IN ("*.exe","*.dll") Object_Type=File Share_Name IN ("\\\\*\\C$","\\\\*\\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)` | `executable_file_written_in_administrative_smb_share_filter`
Associated Analytic Story
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.
Kill Chain Phase
- Lateral Movement
Known False Positives
System Administrators may use looks like PsExec for troubleshooting or administrations tasks. However, this will typically come only from certain users and certain systems that can be added to an allow list.
|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=$Access_Mask$|
source | version: 2