Detect SVG Smuggling in Microsoft Sentinel
Adversaries may smuggle data and files past content filters by hiding malicious payloads inside of seemingly benign SVG files. SVGs are vector-based image files constructed using XML and can legitimately include <script> tags, enabling adversaries to embed malicious JavaScript payloads. SVGs may appear less suspicious to users than other executable file types since they are often treated as image files. SVG smuggling can assemble or download malicious payloads, redirect users to malicious websites, or display interactive content such as fake login forms. SVG Smuggling may be used in conjunction with HTML Smuggling where an SVG with a malicious payload is included inside an HTML file.
MITRE ATT&CK
- Tactic
- Defense Evasion
- Technique
- T1027 Obfuscated Files or Information
- Sub-technique
- T1027.017 SVG Smuggling
- Canonical reference
- https://attack.mitre.org/techniques/T1027/017/
KQL Detection Query
// Detect SVG files opened by browsers or mail clients that subsequently spawn processes or download files
let SuspiciousChildProcesses = dynamic(["cmd.exe", "powershell.exe", "pwsh.exe", "wscript.exe", "cscript.exe", "mshta.exe", "rundll32.exe", "regsvr32.exe", "certutil.exe", "msiexec.exe", "bitsadmin.exe", "curl.exe", "wget.exe"]);
let BrowserProcesses = dynamic(["chrome.exe", "msedge.exe", "firefox.exe", "iexplore.exe", "opera.exe", "brave.exe"]);
let MailClients = dynamic(["outlook.exe", "thunderbird.exe", "winmail.exe"]);
// Detection 1: Browser or mail client spawning suspicious child processes after SVG-related activity
let SvgSpawnedProcesses = DeviceProcessEvents
| where Timestamp > ago(24h)
| where InitiatingProcessFileName has_any (BrowserProcesses) or InitiatingProcessFileName has_any (MailClients)
| where FileName has_any (SuspiciousChildProcesses)
| extend SvgContext = InitiatingProcessCommandLine has ".svg"
| project Timestamp, DeviceName, AccountName, FileName, ProcessCommandLine,
InitiatingProcessFileName, InitiatingProcessCommandLine, SvgContext,
DetectionType = "SuspiciousChildProcess";
// Detection 2: SVG files written to disk by browsers or mail clients
let SvgFileWrites = DeviceFileEvents
| where Timestamp > ago(24h)
| where FileName endswith ".svg"
| where InitiatingProcessFileName has_any (BrowserProcesses) or InitiatingProcessFileName has_any (MailClients)
| project Timestamp, DeviceName, AccountName = InitiatingProcessAccountName,
FileName, FolderPath, InitiatingProcessFileName, InitiatingProcessCommandLine,
SvgContext = true, DetectionType = "SvgFileWrite";
// Detection 3: Script execution from temp/download directories (common SVG payload drop locations)
let SvgPayloadExecution = DeviceProcessEvents
| where Timestamp > ago(24h)
| where FileName has_any (SuspiciousChildProcesses)
| where FolderPath has_any ("\\Downloads\\", "\\Temp\\", "\\AppData\\Local\\Temp\\", "\\AppData\\Roaming\\")
| where InitiatingProcessFileName has_any (BrowserProcesses) or InitiatingProcessFileName has_any (MailClients)
| project Timestamp, DeviceName, AccountName, FileName, ProcessCommandLine, FolderPath,
InitiatingProcessFileName, InitiatingProcessCommandLine,
SvgContext = false, DetectionType = "PayloadFromDownloads";
union SvgSpawnedProcesses, SvgFileWrites, SvgPayloadExecution
| sort by Timestamp descDetects SVG smuggling activity across three patterns: (1) browsers or mail clients spawning suspicious child processes with SVG context in command line, (2) SVG files being written to disk by browsers or mail clients (indicating an SVG attachment or download), and (3) suspicious process execution from common download/temp directories initiated by browser or mail client parent processes. These patterns together cover the primary SVG smuggling delivery and execution chain.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate SVG downloads from design or documentation tools where developers open SVG files normally
- Web development workflows where SVG files are edited and executed locally via browser for testing
- Corporate applications that use SVG icons or graphics and invoke browser rendering legitimately
- Email clients that preview SVG images attached to legitimate business communications
Other platforms for T1027.017
Testing Methodology
Validate this detection against 4 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 and Open Malicious SVG with Embedded JavaScript
Expected signal: Sysmon Event ID 11: File Create — TargetFilename ending in Invoice-2024.svg written to Downloads directory by powershell.exe. Sysmon Event ID 1: Process Create — browser process (e.g., msedge.exe or chrome.exe) launched with the SVG file path as argument. Sysmon Event ID 3: Network Connection — may be generated if browser makes requests after opening file.
- Test 2SVG Smuggling with Blob URL Payload Download Simulation
Expected signal: Sysmon Event ID 11: File Create — document-viewer.svg written to Downloads by powershell.exe. If opened in browser: Sysmon Event ID 11 — browser may write document.exe to Downloads directory. Sysmon Event ID 1 — browser process launch with SVG path. Network telemetry: Blob URL creation stays local (no external network), but browser history records the file:// URI.
- Test 3SVG File Delivered via Email Simulation with Zone Identifier Check
Expected signal: Sysmon Event ID 11: File Create — Invoice_March2024.svg created in Outlook INetCache directory by powershell.exe. Sysmon Event ID 15 (FileCreateStreamHash): ADS Zone.Identifier written to the SVG file, indicating internet-sourced content (Zone=3). This ADS event is a strong indicator of an externally-sourced file.
- Test 4SVG Embedded in HTML File (HTML Smuggling Combination)
Expected signal: Sysmon Event ID 11: File Create — invoice-document.html written to Downloads by powershell.exe. Select-String output confirms presence of <svg>, <script>, atob, and blob indicators in the file. If opened in browser: potential Sysmon Event ID 11 for invoice.exe creation in Downloads.
References (10)
- https://attack.mitre.org/techniques/T1027/017/
- https://blog.talosintelligence.com/html-smugglers-turn-to-svg-images/
- https://www.trustwave.com/en-us/resources/blogs/spiderlabs-blog/pixel-perfect-trap-the-surge-of-svg-borne-phishing-attacks/
- https://www.bleepingcomputer.com/news/security/phishing-emails-increasingly-use-svg-attachments-to-evade-detection/
- https://cofense.com/blog/svg-files-abused-in-emerging-campaigns/
- https://learn.microsoft.com/en-us/microsoft-365/security/defender-endpoint/advanced-hunting-devicefileevents-table
- https://learn.microsoft.com/en-us/microsoft-365/security/defender-endpoint/advanced-hunting-deviceprocessevents-table
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1027.006/T1027.006.md
- https://www.w3.org/TR/SVG2/interact.html#EventAttributes
- https://docs.splunk.com/Documentation/SplunkCloud/latest/SearchReference/CommonStatsFunctions
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