HTML/SVG Attachment HTML Smuggling Spearphishing (T1566.001)
Detects inbound emails containing attachments with file extensions commonly used for HTML/SVG smuggling (.html, .htm, .svg, .shtml, .xhtml). This technique is often used to bypass email security filters by assembling malicious payloads client-side after the email has been delivered. The rule specifically looks for inbound emails where the attachment has not been blocked or junked by the email gateway.
Microsoft Sentinel (KQL)
