Query: ATT&CK technique for Hidden File System
Matching passage: T1564.005 Hidden File System. Tactics: stealth. Description: 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.(Citation: MalwareTech VFS Nov 2014) 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.(Citation: MalwareTech VFS Nov 2014)(Citation: FireEye Bootkits) Another implementation could be for an adversary to drop their own portable partition image as a file on top of the standard file system.(Citation: ESET ComRAT May 2020) Adversaries may also fragment files across the existing file system structure in non-standard ways.(Citation: Kaspersky Equation QA)
Near-miss passage: T1564.006 Run Virtual Instance. Tactics: stealth. Description: Adversaries may carry out malicious operations using a virtual instance to avoid detection. A wide variety of virtualization technologies exist that allow for the emulation of a computer or computing environment. By running malicious code inside of a virtual instance, adversaries can hide artifacts associated with their behavior from security tools that are unable to monitor activity inside the virtual instance.(Citation: CyberCX Akira Ransomware) Additionally, depending on the virtual networking implementation (ex: bridged adapter), network traffic generated by the virtual instance can be difficult to trace back to the compromised host as the IP address and hostname might not match known values.(Citation: SingHealth Breach Jan 2019) Adversaries may utilize native support for virtualization (ex: Hyper-V), deploy lightweight emulators (ex: QEMU), or drop the necessary files to run a virtual instance (ex: VirtualBox binaries).(Citation: Securonix CronTrap 2024) After running a virtual instance, adversaries may create a shared folder between the guest and host with permissions that enable the virtual instance to interact with the host file system.(Citation: Sophos Ragnar May 2020) Threat actors may also leverage temporary virtualized environments such as the Windows Sandbox, which supports the use of `.wsb` configuration files for defining execution parameters. For example, the `<MappedFolder>` property supports the creation of a shared folder, while the `<LogonCommand>` property allows the specification of a payload.(Citation: ESET MirrorFace 2025)(Citation: ITOCHU Hack the Sandbox)(Citation: ITOCHU Sandbox PPT) In VMWare environments, adversaries may leverage the vCenter console to create new virtual machines. However, they may also create virtual machines directly on ESXi servers by running a valid `.vmx` file with the `/bin/vmx` utility. Adding this command to `/etc/rc.local.d/local.sh` (i.e., [RC Scripts](https://attack.mitre.org/techniques/T1037/004)) will cause