Suspicious Disk Image File Written by a Browser or Mail Client (via file_event)
- Product
- windows
- Category
- file_event
- Author
- HuntRule
- Published
- 2026-06-04
- Updated
- 2026-08-28
ATT&CK techniques
Defense EvasionRecon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact
What it detects
This rule detects a browser or email client writing an ISO, IMG or VHD disk-image file to disk, the delivery half of an HTML-smuggling campaign that packages a payload inside a container to bypass Mark-of-the-Web and mail-attachment controls. HTML smuggling and container-file delivery are recurring initial-access techniques in the Red Canary Threat Detection Report. Detecting image files dropped by internet-facing apps surfaces smuggled payloads before they are mounted and run.
Reporting behind it
Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.
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Also included
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