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T1553.005 Mark-of-the-Web Bypass

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.4 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.123

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.12

Item Value
ID T1553.005
Sub-techniques T1553.001, T1553.002, T1553.003, T1553.004, T1553.005, T1553.006
Tactics TA0005
Platforms Windows
Version 1.1
Created 22 February 2021
Last Modified 22 March 2023

Procedure Examples

ID Name Description
S1025 Amadey Amadey has modified the :Zone.Identifier in the ADS area to zero.8
G0016 APT29 APT29 has embedded ISO images and VHDX files in HTML to evade Mark-of-the-Web.10
S0650 QakBot QakBot has been packaged in ISO files in order to bypass Mark of the Web (MOTW) security measures.9
G0092 TA505 TA505 has used .iso files to deploy malicious .lnk files.11


ID Mitigation Description
M1042 Disable or Remove Feature or Program Consider disabling auto-mounting of disk image files (i.e., .iso, .img, .vhd, and .vhdx). This can be achieved by modifying the Registry values related to the Windows Explorer file associations in order to disable the automatic Explorer “Mount and Burn” dialog for these file extensions. Note: this will not deactivate the mount functionality itself.6
M1038 Execution Prevention Consider blocking container file types at web and/or email gateways. Consider unregistering container file extensions in Windows File Explorer.7


ID Data Source Data Component
DS0022 File File Creation