Subvert Trust Controls: Mark-of-the-Web Bypass T1553.005
Tactic: Defense Impairment
Adversaries may abuse specific file formats to subvert Mark-of-the-Web (MOTW) controls. In Windows, when files are downloaded from the Internet, they are tagged with a hidden NTFS Alternate Data Stream (ADS) named Zone.Identifier with a specific value known as the MOTW. Files that are tagged with MOTW are protected and cannot perform certain actions. For example, starting in MS Office 10, if a MS Office file has the MOTW, it will open in Protected View. Executables tagged with the MOTW will be processed by Windows Defender SmartScreen that compares files with an allowlist of well-known executables. If the file is not known/trusted, SmartScreen will prevent the execution and warn the user not to run it.
Events covered
9 catalog events are tagged with this technique by at least one rule.
Authoring guide
Patterns shared across the 13 rules above: which fields they filter on, what specific values they look for, and what they exclude. The catalog normalizes field names across vendors so Sigma's Image, Elastic's process.name, and Splunk's process_name collapse into one row. Each rule contributes at most once per row.
Fields filtered most (10 distinct)
The fields most rules look at when detecting this technique. The How column shows the operators authors use (eq, wildcard, regex_match, match) and how often each appears. Sample values are concrete examples to start from, not an exhaustive list.
Top indicator values (37 distinct)
Specific (field, operator, value) combinations the rules check for, ranked by how many rules under this technique use each one. The Corpus reach column counts how many rules across the entire catalog (any technique) check the same combination. High numbers point to widely-used indicators that are likely noisy on their own; combine them with another condition for useful signal. Blank means the combination is specific to rules under this technique. Click a value to expand the rules under this technique that use it.
Exclusions (12 distinct)
Field/operator/value combinations excluded by rules under this technique (top-level not() clauses), sorted by how many rules exclude each. These are the false-positive paths the community has learned to filter out. A new rule that ignores the high-count entries here will likely fire on the same noisy paths. Click a value to expand the rules under this technique that exclude it.
Rules under this technique
Every rule in the catalog tagged with this technique, grouped by vendor. Click a rule title for its full predicates, exclusions, and indicators.
Sigma 6 rules
- Suspicious Invoke-Item From Mount-DiskImage
- Suspicious Mount-DiskImage
- Suspicious Unblock-File
- Windows AppX Deployment Full Trust Package Installation
- Windows AppX Deployment Unsigned Package Installation
- Windows MSIX Package Support Framework AI_STUBS Execution
Splunk 7 rules
- ISO Image Mounted - Windows (PowerShell)
- ISO Image Mounted - Windows (Windows Event Log)
- Windows Advanced Installer MSIX with AI_STUBS Execution
- Windows AppX Deployment Full Trust Package Installation
- Windows AppX Deployment Unsigned Package Installation
- Windows Developer-Signed MSIX Package Installation
- Windows Mark Of The Web Bypass