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Subvert Trust Controls: Mark-of-the-Web Bypass

ID Name
T1553.001 Gatekeeper Bypass
T1553.002 Code Signing
T1553.003 SIP and Trust Provider Hijacking
T1553.004 Install Root Certificate
T1553.005 Mark-of-the-Web Bypass
T1553.006 Code Signing Policy Modification

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.[1] 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.[2][3][4]

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.[2][3]

ID: T1553.005
Sub-technique of:  T1553
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Tactic: Defense Evasion
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Platforms: Windows
Contributors: Christiaan Beek, @ChristiaanBeek
Version: 1.2
Created: 22 February 2021
Last Modified: 24 October 2025
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Procedure Examples

ID Name Description
S1025 Amadey

Amadey has modified the :Zone.Identifier in the ADS area to zero.[5]
G0016 APT29

APT29 has embedded ISO images and VHDX files in HTML to evade Mark-of-the-Web.[6]
G0082 APT38

APT38 has used ISO and VHD files to deploy malware and to bypass Mark-of-the-Web (MOTW) security measures.[7]

S0650 QakBot

QakBot has been packaged in ISO files in order to bypass Mark of the Web (MOTW) security measures.[8]
G0092 TA505

TA505 has used .iso files to deploy malicious .lnk files.[9]

Mitigations

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.[10]
M1038 Execution Prevention

Consider blocking container file types at web and/or email gateways. Consider unregistering container file extensions in Windows File Explorer.[11]

Detection Strategy

ID Name Analytic ID Analytic Description
DET0257 Detect Mark-of-the-Web (MOTW) Bypass via Container and Disk Image Files AN0712

Detects extraction or mounting of container/archive files (e.g., .iso, .vhd, .zip) that originated from the Internet but whose contained files lack Zone.Identifier MOTW tagging. Correlates file creation metadata with subsequent execution of unsigned or untrusted binaries launched outside SmartScreen or Protected View.

References

  1. Microsoft. (2020, August 31). Zone.Identifier Stream Name. Retrieved February 22, 2021.
  2. Beek, C. (2020, December 3). Investigating the Use of VHD Files By Cybercriminals. Retrieved November 17, 2024.
  3. Hegt, S. (2020, March 30). Mark-of-the-Web from a red team’s perspective. Retrieved February 22, 2021.
  4. Kennedy, J. (2020, December 9). A Zebra in Gopher's Clothing: Russian APT Uses COVID-19 Lures to Deliver Zebrocy. Retrieved February 22, 2021.
  5. Financial Security Institute. (2020, February 28). Profiling of TA505 Threat Group That Continues to Attack the Financial Sector. Retrieved July 14, 2022.
  6. ESET. (2022, February). THREAT REPORT T3 2021. Retrieved February 10, 2022.
  1. SEONGSU PARK. (2022, December 27). BlueNoroff introduces new methods bypassing MoTW. Retrieved February 6, 2024.
  2. Kenefick, I. et al. (2022, October 12). Black Basta Ransomware Gang Infiltrates Networks via QAKBOT, Brute Ratel, and Cobalt Strike. Retrieved February 6, 2023.
  3. Trend Micro. (2019, August 27). TA505: Variety in Use of ServHelper and FlawedAmmyy. Retrieved February 22, 2021.
  4. wdormann. (2019, August 29). Disable Windows Explorer file associations for Disc Image Mount. Retrieved April 16, 2022.
  5. Dormann, W. (2019, September 4). The Dangers of VHD and VHDX Files. Retrieved March 16, 2021.