Detect Replication Through Removable Media in Elastic Security
Adversaries may move onto systems, possibly those on disconnected or air-gapped networks, by copying malware to removable media and taking advantage of Autorun features when the media is inserted into a system. This technique serves dual purposes: Initial Access (introducing malware into isolated or air-gapped environments) and Lateral Movement (propagating between networked systems via USB). Common implementations include creating autorun.inf files that auto-execute malware on media insertion, copying malicious executables to the drive root disguised as legitimate files, and creating LNK shortcut files that silently execute hidden payloads. Notable threat actors include Stuxnet (targeting air-gapped ICS/SCADA networks via CVE-2010-2568 LNK vulnerability), Flame (modular USB infection framework), Gamaredon Group (LNK files on all removable and network drives via UserAssist persistence), Mustang Panda and APT30 (customized PlugX USB variants), Raspberry Robin (worm spread via infected USB media), HIUPAN (periodic drive polling for propagation), and Aoqin Dragon (removable device dropper for breaching secure network environments).
MITRE ATT&CK
- Tactic
- Lateral Movement Initial Access
- Canonical reference
- https://attack.mitre.org/techniques/T1091/
Elastic Detection Query
any where
(
/* Signal 1: autorun.inf creation on non-system drive */
(event.category == "file" and event.action in ("creation", "change") and
file.name : "autorun.inf" and
file.path : ("[D-Zd-z]:\\*") and
not file.path : "\\\\*")
or
/* Signal 2: Executable at root of non-system drive */
(event.category == "file" and event.action in ("creation", "change") and
file.extension : ("exe", "dll", "bat", "cmd", "vbs", "js", "lnk", "hta", "ps1", "scr", "pif", "com") and
file.path : ("[D-Zd-z]:\\*") and
not file.path : ("[D-Zd-z]:\\*\\*") and
not file.path : "\\\\*")
or
/* Signal 3: Executable written to removable media by unexpected process */
(event.category == "file" and event.action in ("creation", "change") and
file.extension : ("exe", "dll", "bat", "cmd", "vbs", "js", "lnk", "hta", "ps1", "scr", "pif", "com") and
file.path : ("[D-Zd-z]:\\*") and
not file.path : "\\\\*" and
not process.name : ("explorer.exe", "robocopy.exe", "xcopy.exe", "msiexec.exe", "setup.exe", "install.exe", "installer.exe"))
or
/* Signal 4: Process launched directly from non-system drive */
(event.category == "process" and event.type == "start" and
process.executable : ("[D-Zd-z]:\\*") and
not process.executable : "\\\\*")
)Detects replication through removable media (T1091) by monitoring four signals: autorun.inf creation on non-system drives, executables/scripts written to drive roots, suspicious executables written to removable media by unexpected processes, and processes launched directly from non-system drives. Covers Stuxnet, Flame, PlugX, Raspberry Robin, and Aoqin Dragon patterns.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate software installers or update packages written to USB drives by IT staff for deployment to isolated systems
- Backup agents (e.g., Acronis, Veeam) copying executable images to external drives as part of scheduled backup jobs
- Portable application launchers (PortableApps.com suite) that legitimately execute applications from non-system drives and may place LNK files at drive roots
Other platforms for T1091
Testing Methodology
Validate this detection against 5 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Create autorun.inf on Non-System Drive
Expected signal: Sysmon Event ID 11 (File Create): TargetFilename=D:\autorun.inf, Image=cmd.exe. DeviceFileEvents in MDE: FileName=autorun.inf, FolderPath=D:\, ActionType=FileCreated, InitiatingProcessFileName=cmd.exe.
- Test 2Copy Executable to Removable Drive Root (PlugX/HIUPAN Pattern)
Expected signal: Sysmon Event ID 11 (File Create): TargetFilename=D:\system_update.exe, Image=cmd.exe, MD5 matches cmd.exe hash. DeviceFileEvents in MDE: FileName=system_update.exe, FolderPath=D:\, ActionType=FileCreated, SHA256 matches cmd.exe.
- Test 3Create Malicious LNK Shortcut on Removable Drive (Gamaredon Technique)
Expected signal: Sysmon Event ID 11 (File Create): TargetFilename=D:\Documents.lnk, Image=powershell.exe. DeviceFileEvents in MDE: FileName=Documents.lnk, FolderPath=D:\, ActionType=FileCreated, InitiatingProcessFileName=powershell.exe. WindowStyle=7 (minimized/hidden window) indicates deliberate concealment.
- Test 4Execute Process Directly from Removable Drive
Expected signal: Sysmon Event ID 1 (Process Create): Image=D:\usb_payload.exe, CommandLine=D:\usb_payload.exe /C whoami, ParentImage=cmd.exe. DeviceProcessEvents in MDE: FileName=usb_payload.exe, FolderPath=D:\, ProcessCommandLine contains 'whoami'. Preceded by Sysmon Event ID 11 for the file copy.
- Test 5Enumerate Removable Drives via WMI (USB Worm Reconnaissance)
Expected signal: Sysmon Event ID 1 (Process Create): Image=powershell.exe, CommandLine contains 'Win32_LogicalDisk' and 'DriveType'. DeviceProcessEvents in MDE: FileName=powershell.exe, ProcessCommandLine contains WMI query. WMI Activity log (Microsoft-Windows-WMI-Activity/Operational Event ID 5857/5858) may record the Win32_LogicalDisk query.
References (10)
- https://attack.mitre.org/techniques/T1091/
- https://securelist.com/the-flame-malware/73765/
- https://symantec-enterprise-blogs.security.com/blogs/threat-intelligence/shuckworm-usb-threat-ukraine
- https://www.threatexpert.com/report.aspx?md5=4c48f0dc5c55e26d5b68dfafe2e54b31
- https://www.trendmicro.com/en_us/research/22/f/raspberry-robin-worming-its-way-through-networks.html
- https://www.sentinelone.com/labs/aoqin-dragon-newly-discovered-chinese-linked-apt-has-been-quietly-spying-on-organizations-for-10-years/
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1091/T1091.md
- https://learn.microsoft.com/en-us/windows/security/operating-system-security/device-management/control-usb-devices-using-intune
- https://learn.microsoft.com/en-us/defender-endpoint/advanced-hunting-devicefileevents-table
- https://docs.microsoft.com/en-us/windows/security/threat-protection/auditing/event-4663
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