Hide Artifacts: Hidden File System

Adversaries may use a hidden file system to conceal malicious activity from users and security tools. File systems provide a structure to store and access data from physical storage. Typically, a user engages with a file system through applications that allow them to access files and directories, which are an abstraction from their physical location (ex: disk sector). Standard file systems include FAT, NTFS, ext4, and APFS. File systems can also contain other structures, such as the Volume Boot Record (VBR) and Master File Table (MFT) in NTFS.[1]

Adversaries may use their own abstracted file system, separate from the standard file system present on the infected system. In doing so, adversaries can hide the presence of malicious components and file input/output from security tools. Hidden file systems, sometimes referred to as virtual file systems, can be implemented in numerous ways. One implementation would be to store a file system in reserved disk space unused by disk structures or standard file system partitions.[1][2] Another implementation could be for an adversary to drop their own portable partition image as a file on top of the standard file system.[3] Adversaries may also fragment files across the existing file system structure in non-standard ways.[4]

ID: T1564.005
Sub-technique of:  T1564
Tactic: Defense Evasion
Platforms: Linux, Windows, macOS
Permissions Required: Administrator, User
Version: 1.0
Created: 28 June 2020
Last Modified: 29 June 2020

Procedure Examples

ID Name Description

BOOTRASH has used unallocated disk space between partitions for a hidden file system that stores components of the Nemesis bootkit.[2]

S0126 ComRAT

ComRAT has used a portable FAT16 partition image placed in %TEMP% as a hidden file system.[3]

G0020 Equation

Equation has used an encrypted virtual file system stored in the Windows Registry.[4]

S0019 Regin

Regin has used a hidden file system to store some of its components.[5]

G0041 Strider

Strider has used a hidden file system that is stored as a file on disk.[6]

S0022 Uroburos

Uroburos can use concealed storage mechanisms including an NTFS or FAT-16 filesystem encrypted with CAST-128 in CBC mode.[7]


This type of attack technique cannot be easily mitigated with preventive controls since it is based on the abuse of system features.


ID Data Source Data Component Detects
DS0022 File File Modification

Detecting the use of a hidden file system may be exceptionally difficult depending on the implementation. Emphasis may be placed on detecting related aspects of the adversary lifecycle, such as how malware interacts with the hidden file system or how a hidden file system is loaded.

DS0001 Firmware Firmware Modification

Monitor for changes made to firmware for unexpected modifications to settings and/or data that may use a hidden file system to conceal malicious activity from users and security tools. Bootkit

DS0024 Windows Registry Windows Registry Key Modification

Monitor for changes made to windows registry keys and/or values that may use a hidden file system to conceal malicious activity from users and security tools.