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Description

The following analytic identifies object access on Windows administrative SMB shares (Admin$, IPC$, C$). This represents suspicious behavior as its commonly used by tools 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 IcedID malware family also implements this behavior to try to infect other machines in the infected network.

  • Type: Hunting

  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2023-05-23
  • Author: Teoderick Contreras, Splunk
  • ID: dc1457d0-1d9b-422e-b5a7-db46c184d9aa

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1135 Network Share Discovery Discovery
Kill Chain Phase
  • Exploitation
NIST
  • DE.AE
CIS20
  • CIS 10
CVE 


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`wineventlog_security` EventCode=5140 ShareName IN("\\\\*\\ADMIN$","\\\\*\\C$","*\\\\*\\IPC$") AccessMask= 0x1 
| stats min(_time) as firstTime max(_time) as lastTime count by ShareName IpAddress ObjectType SubjectUserName SubjectDomainName IpPort AccessMask Computer 
| rename Computer as dest 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `network_share_discovery_via_dir_command_filter`

Macros

The SPL above uses the following Macros:

:information_source: network_share_discovery_via_dir_command_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • ShareName
  • IpAddress
  • ObjectType
  • SubjectUserName
  • SubjectDomainName
  • IpPort
  • AccessMask
  • Computer

How To Implement

To successfully implement this search, you need to be ingesting Windows Security Event Logs with 5140 EventCode enabled. The Windows TA is also required. Also enable the object Audit access success/failure in your group policy.

Known False Positives

System Administrators may use looks like net.exe or "dir commandline" 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.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
25.0 50 50 $user$ list executable files or directory in known sensitive SMB share. Share name=$ShareName$, Access mask=$AccessMask$

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

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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