> For the complete documentation index, see [llms.txt](https://dmcxblue.gitbook.io/red-team-notes-2-0/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://dmcxblue.gitbook.io/red-team-notes-2-0/red-team-techniques/defense-evasion/t1564-hide-artifacts/hidden-file-system.md).
# 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 NFTS.
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. Another implementation could be for an adversary to drop their own portable partition image as a file on top of the standard file system. Adversaries may also fragment files across the existing file system structure in non-standard ways.
Building a file system is straightforward will use the truncate command as this builds a file system that expands dynamically, and continue with using the mfks.EXT to build it
We can proceed to mount the file system and with some creativity place it in a random location while utilizing some techniques for concealing directories.
---
# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.
## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.
Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:
```
GET https://dmcxblue.gitbook.io/red-team-notes-2-0/red-team-techniques/defense-evasion/t1564-hide-artifacts/hidden-file-system.md?ask=&goal=
```
`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.