Detect SVG Smuggling in CrowdStrike LogScale
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/
LogScale Detection Query
#event_simpleName=ProcessRollup2
| ParentBaseFileName = /(?i)(chrome|msedge|firefox|iexplore|opera|brave|outlook|thunderbird|winmail)\.exe/
| FileName = /(?i)(cmd|powershell|pwsh|wscript|cscript|mshta|rundll32|regsvr32|certutil|msiexec|bitsadmin|curl|wget)\.exe/
| SvgInCommandLine := if(
CommandLine = /(?i)\.svg/ OR ParentCommandLine = /(?i)\.svg/,
"true", "false"
)
| DropPathLaunch := if(
CommandLine = /(?i)(downloads|\\temp\\|appdata)/,
"true", "false"
)
| RiskScore := if(SvgInCommandLine = "true", 2, 1) + if(DropPathLaunch = "true", 1, 0)
| DetectionType := case(
SvgInCommandLine = "true" AND DropPathLaunch = "true", "SVG_Smuggling_High_Confidence",
SvgInCommandLine = "true", "SVG_Context_Suspicious_Spawn",
DropPathLaunch = "true", "Suspicious_Spawn_From_Drop_Path",
true(), "Browser_Mail_Spawned_Suspicious_Process"
)
| select([timestamp, ComputerName, UserName, FileName, CommandLine, ParentBaseFileName, ParentCommandLine, SvgInCommandLine, DropPathLaunch, RiskScore, DetectionType])
| sort(timestamp, order=desc)Detects SVG Smuggling (T1027.017) in CrowdStrike Falcon using LogScale (Humio) CQL against ProcessRollup2 telemetry. Filters for browser and mail client processes (ParentBaseFileName) that spawn suspicious child processes (FileName) consistent with LOLBin abuse or script interpreter execution. Enriches each match with two derived boolean fields: SvgInCommandLine (true if .svg appears in the child or parent command line, indicating direct SVG payload context) and DropPathLaunch (true if the command line references common malware drop directories). A composite RiskScore and four-tier DetectionType classification assist analyst triage. Relies on Falcon's native process lineage telemetry which accurately captures parent-child relationships at the kernel level.
Data Sources
Required Tables
False Positives & Tuning
- Browser-initiated installer workflows where the user clicks 'Run' on a downloaded file from Chrome or Edge, causing the browser to spawn msiexec.exe or a setup executable — extremely common in enterprise environments without application whitelisting.
- Password managers or corporate SSO browser extensions (1Password, LastPass, Okta Verify) that inject into browser processes and occasionally invoke PowerShell for credential database sync or system keychain integration.
- Development workstations where engineers use browser-based tools (GitHub Codespaces browser tab, Jupyter notebooks served locally) that legitimately spawn cmd.exe or curl.exe for build automation or notebook kernel management.
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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