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
Suspicious Access to Citrix Session Evidence Registry Keys
Suspicious Ransomware Fan-Out Deployment via PsExec Spread (Qilin)
Suspicious Impacket smbexec Command Execution Pattern
Malicious Impacket Wmiexec Remote Command Execution Pattern
Suspicious Remote Admin Share Execution via Conhost
Malicious Network Share Manipulation via Commandline (via process_creation)
Suspicious Number of Oustanding SMB Requests Increased (via process_creation)
Suspicious SMB Insecure Guest Authentication Activated - Native (via security)
Suspicious PSexec Execution Over SMB Share (via security)
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.