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Upgrade to ProDetect LNK Icon Smuggling in Microsoft Sentinel
This detection identifies adversary abuse of Windows shortcut (.LNK) file metadata — specifically the IconEnvironmentDataBlock (icon location field) and target path field — to smuggle commands or URLs that download malicious payloads. Threat actors including Kimsuky, Gamaredon Group, and Mustang Panda have leveraged crafted LNK files delivered via phishing or USB to execute scripts and binaries while displaying benign icons (e.g., PDF, Word document). Detection focuses on LNK files spawning unusual child processes, network connections originating from LNK-invoked interpreters, suspicious icon paths pointing to remote UNC or HTTP locations, and command-line interpreters launched with padded or obfuscated arguments consistent with LNK target field abuse.
MITRE ATT&CK
- Tactic
- Defense Evasion
- Technique
- T1027 Obfuscated Files or Information
- Sub-technique
- T1027.012 LNK Icon Smuggling
- Canonical reference
- https://attack.mitre.org/techniques/T1027/012/
KQL Detection Query
let LNKSpawnedInterpreters = DeviceProcessEvents
| where InitiatingProcessFileName =~ "explorer.exe" or InitiatingProcessCommandLine has ".lnk"
| where FileName in~ ("powershell.exe", "cmd.exe", "wscript.exe", "cscript.exe", "mshta.exe", "rundll32.exe", "regsvr32.exe", "certutil.exe", "curl.exe", "bitsadmin.exe")
| where ProcessCommandLine has_any ("http://", "https://", "ftp://", "\\\\")
or ProcessCommandLine matches regex @"(?i)(iex|invoke-expression|downloadstring|downloadfile|webclient|wget|curl)"
| project TimeGenerated, DeviceName, AccountName, InitiatingProcessFileName, InitiatingProcessCommandLine, FileName, ProcessCommandLine, FolderPath, SHA256, InitiatingProcessSHA256;
let LNKNetworkActivity = DeviceNetworkEvents
| where InitiatingProcessFileName in~ ("powershell.exe", "cmd.exe", "wscript.exe", "cscript.exe", "mshta.exe")
| where InitiatingProcessCommandLine has ".lnk" or RemoteUrl has_any (".ps1", ".vbs", ".bat", ".hta", ".exe", ".dll")
| where RemoteIPType != "Private"
| project TimeGenerated, DeviceName, AccountName, InitiatingProcessFileName, InitiatingProcessCommandLine, RemoteIP, RemoteUrl, RemotePort;
LNKSpawnedInterpreters
| union LNKNetworkActivity
| order by TimeGenerated descDetects LNK files invoking command interpreters or download utilities with external URLs or UNC paths in the process command line, and network connections from LNK-spawned scripting hosts to external IPs delivering executable payloads.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate LNK shortcuts that reference network shares for shared software installations (e.g., corporate app deployment via UNC paths)
- IT management tools that create LNK files pointing to administrative scripts hosted on internal web servers
- Software update agents that use shortcut files to trigger PowerShell-based update checks against known-good URLs
Other platforms for T1027.012
Testing Methodology
Validate this detection against 3 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 1LNK Icon Path URL Trigger via PowerShell Download
Expected signal: DeviceProcessEvents: powershell.exe spawned by explorer.exe with -WindowStyle Hidden and DownloadString URL; DeviceNetworkEvents: outbound connection from powershell.exe to 127.0.0.1:8080; Sysmon Event ID 11: LNK file creation in %TEMP%; Sysmon Event ID 3: network connection from powershell.exe
- Test 2LNK Target Field Padding to Bypass Visual Inspection
Expected signal: Sysmon Event ID 1 or Security Event ID 4688: cmd.exe spawned by explorer.exe; CommandLine field showing /c echo command with 300+ trailing spaces; Sysmon Event ID 11: lnk_test_output.txt created in %TEMP%
- Test 3LNK File Executing mshta for Remote HTA Payload
Expected signal: DeviceProcessEvents: mshta.exe spawned by explorer.exe with HTTP URL argument; DeviceNetworkEvents: outbound HTTP GET from mshta.exe to 127.0.0.1:8080; Sysmon Event ID 1: mshta.exe with command line containing http://; Sysmon Event ID 3: network connection from mshta.exe process
References (5)
- https://attack.mitre.org/techniques/T1027/012/
- https://unprotect.it/technique/shortcut-icon-smuggling/
- https://blog.talosintelligence.com/mustang-panda-targets-europe/
- https://www.mandiant.com/resources/blog/lnk-icon-smuggling-technique
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1027.012/T1027.012.md
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