Mark-of-the-Web Bypass

Executive Summary

Mark-of-the-Web Bypass (T1553.005) is a MITRE ATT&CK technique associated with Defense Impairment. Adversaries may abuse specific file formats to subvert Mark-of-the-Web (MOTW) controls.

Why Attackers Use It

Attackers use Mark-of-the-Web Bypass because it provides a reliable way to advance their objective within the Defense Impairment tactic, often with a favorable balance of impact versus detectability on Windows environments. Defenders should assess this behavior in the context of the affected platform and adjacent activity rather than treating it as a standalone indicator.

MITRE Description

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 <code>Zone.Identifier</code> with a specific value known as the MOTW.(Citation: Microsoft Zone.Identifier 2020) 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.(Citation: Beek Use of VHD Dec 2020)(Citation: Outflank MotW 2020)(Citation: Intezer Russian APT Dec 2020)

Adversaries may abuse container files such as compressed/archive (.arj, .gzip) and/or disk image (.iso, .vhd) file formats to deliver malicious payloads that may not be tagged with MOTW. Container files downloaded from the Internet will be marked with MOTW but the files within may not inherit the MOTW after the container files are extracted and/or mounted. MOTW is a NTFS feature and many container files do not support NTFS alternative data streams. After a container file is extracted and/or mounted, the files contained within them may be treated as local files on disk and run without protections.(Citation: Beek Use of VHD Dec 2020)(Citation: Outflank MotW 2020)

Attack Flow

1. Attacker gains the prerequisite access or context described below.
2. Attacker executes Mark-of-the-Web Bypass to achieve its tactical objective (Defense Impairment).
3. Resulting access/data/effect is leveraged to advance the broader attack chain (see Related Techniques).

Prerequisites

• Platform(s): Windows
• ATT&CK does not define one universal permission requirement for this technique. Establish the required access from the observed implementation and affected platform.

Common Tools

• Tool attribution is implementation-specific. Use ATT&CK procedure examples and local telemetry to identify the binaries, services, scripts, accounts, or cloud resources involved.

Commands

No universal command represents Mark-of-the-Web Bypass. Capture the exact command line, arguments, parent process, account, host, and execution time from the investigated environment; do not operationalize unverified examples.

Network Traffic

• Network observability is implementation-dependent. Review DNS, proxy, firewall, flow, authentication, and packet telemetry around the activity window, then correlate remote endpoints and protocol behavior with host evidence.

Windows Events

Sysmon Events

Detection Opportunities

No MITRE detection guidance published for this technique.

Relevant ATT&CK Data Sources: N/A

Sigma Rules

A universal Sigma rule would create unreliable results because this technique has no single guaranteed observable. Build detection logic from a documented behavior and supported data source, scope it to the affected platform, and validate it against benign administrative activity before deployment.

Splunk Queries

Start with the data sources named in the detection section. Scope searches by asset, identity, and time window; correlate the primary behavior with preceding access and subsequent actions. A portable query is intentionally not provided where the technique lacks a universal schema or observable.

Investigation Workflow

1. Confirm that the observed behavior is consistent with Mark-of-the-Web Bypass and rule out expected administrative or application activity.
2. Establish the first-seen time, initiating identity, source system, target system, and affected resources.
3. Collect relevant host, identity, network, cloud, and application telemetry for the surrounding time window.
4. Correlate parent and child activity, remote connections, file or configuration changes, and related ATT&CK techniques.
5. Determine scope by searching for the same observable across peer assets and identities.
6. Preserve volatile evidence and record confidence, assumptions, and telemetry gaps before containment.

Containment

1. Isolate affected host(s)/account(s) identified during investigation.
2. Revoke or rotate any credentials/tokens potentially exposed.
3. Apply the mitigations listed below where not already enforced.
4. Validate no related techniques (see Related Techniques) were chained against the same asset.

Mitigation

• M1042 -- Disable or Remove Feature or Program: Disable or remove unnecessary and potentially vulnerable software, features, or services to reduce the attack surface and prevent abuse by adversaries.
• M1038 -- Execution Prevention: Prevent the execution of unauthorized or malicious code on systems by implementing application control, script blocking, and other execution prevention mechanisms.

Related Techniques

• T1071.001
• T1105
• T1106
• T1112
• T1140
• T1553
• T1568.001