huntrule

Windows Security Event 5145: SMB Write Access to Admin Share (C$)

Flags non-machine accounts writing via SMB to the C$ administrative share using Security EventID 5145.

FreeReviewedSigma · High · v2
Product
windows
Service
security
Author
Jose Rodriguez (@Cyb3rPandaH), OTR (Open Threat Research) (SigmaHQ), DRL 1.1
Published
2020-08-06
Updated
2026-07-31
AnalysisDetection

ATT&CK techniques

Lateral Movement

  1. Recon

  2. Resource Dev

  3. Initial Access

  4. Execution

  5. Persistence

  6. Priv Esc

  7. Defense Evasion

  8. Cred Access

  9. Discovery

  10. Lateral Movement

  11. Collection

  12. C2

  13. Exfiltration

  14. Impact

What it detects

This rule identifies Windows SMB file access attempts that write to an administrative share by matching Security Event 5145 with a ShareName ending in C$ and an AccessMask of 0x2. It focuses on non-computer accounts by excluding SubjectUserName values that end with $. Such write access to admin shares is significant because it can indicate remote file creation or preparation for lateral movement, and it relies on detailed SMB auditing events from Windows Security logs (EventID 5145) including ShareName, AccessMask, and SubjectUserName.

Reporting behind it

Related detections9 linkedT1021.002 — drag to rearrange
Malicious NetExec SMB Enumeration Execution (via process_creation)
Malicious WMIexec Style Command Output Redirection to Local Admin Share
Malicious Cobalt Strike Default Named Pipe Activity
Suspicious PsExec Service Launching Encoded PowerShell Payload
Suspicious Impacket Style Command Execution with ADMIN Share Output Redirect
Suspicious Active Directory Reconnaissance via In-Memory Offensive PowerShell (via ps_script)
Suspicious NetExec Post-Exploitation Tool Execution via nxc (via process_creation)
Suspicious SMB Admin Share Mapping for Lateral Tool Transfer (via process_creation)
Suspicious Impacket Remote Execution Tool Usage via process_creation
Windows Security Event 5145: SMB Write Access to Admin Share (C$)
Pivot detection · T1021.002 · 9 related

Changelog

v2
  1. v2
    Candidate ingested via manual entry.2026-07-31
  2. v1
    No changelog recorded for this version.2026-07-30

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.