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Windows Alternate Data Stream Created Over Local Share

The following analytic detects the creation of an NTFS alternate data stream (ADS) accessed over a local administrative share targeting the loopback address (127.0.0.1). It leverages Windows Security Event Logs with…

Description

The following analytic detects the creation of an NTFS alternate data stream (ADS) accessed over a local administrative share targeting the loopback address (127.0.0.1). It leverages Windows Security Event Logs with EventCode 5145 to identify this activity. Legitimate local processes access files directly rather than through a local SMB share. This behavior is a hallmark of the ShieldBreak exploit, which abuses a symbolic link swap through a loopback share to redirect a privileged, Defender-driven write into an alternate data stream on a system-owned file, ultimately landing attacker content in C:\Windows\System32. If confirmed malicious, this activity indicates an in-progress local privilege escalation attempt and should be investigated immediately.

Detection logic

Detection requirements

Platform
Windows

The rule states no platform. This is derived from the 2 ATT&CK techniques it maps to.

Known benign triggers

  • Backup, replication, or file-sync software may occasionally write alternate data streams over administrative shares. Loopback (127.0.0.1) access to a local share is rare for legitimate software, tune by ShareName or src_user as needed for your environment.

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