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)
Platforms
Threat Groups (2)
| ID | Group | Context |
|---|---|---|
| G0020 | Equation | [Equation](https://attack.mitre.org/groups/G0020) has used an encrypted virtual file system stored in the Windows Registry.(Citation: Kaspersky Equati... |
| G0041 | Strider | [Strider](https://attack.mitre.org/groups/G0041) has used a hidden file system that is stored as a file on disk.(Citation: Kaspersky ProjectSauron Ful... |
Associated Software (4)
| ID | Name | Type | Context |
|---|---|---|---|
| S0126 | ComRAT | Malware | [ComRAT](https://attack.mitre.org/software/S0126) has used a portable FAT16 partition image placed in %TEMP% as a hidden file system.(Citation: ESET C... |
| S0019 | Regin | Malware | [Regin](https://attack.mitre.org/software/S0019) has used a hidden file system to store some of its components.(Citation: Kaspersky Regin) |
| S0114 | BOOTRASH | Malware | [BOOTRASH](https://attack.mitre.org/software/S0114) has used unallocated disk space between partitions for a hidden file system that stores components... |
| S0022 | Uroburos | Malware | [Uroburos](https://attack.mitre.org/software/S0022) can use concealed storage mechanisms including an NTFS or FAT-16 filesystem encrypted with CAST-12... |
References
- Andonov, D., et al. (2015, December 7). Thriving Beyond The Operating System: Financial Threat Group Targets Volume Boot Record. Retrieved May 13, 2016.
- Faou, M. (2020, May). From Agent.btz to ComRAT v4: A ten-year journey. Retrieved June 15, 2020.
- Hutchins, M. (2014, November 28). Virtual File Systems for Beginners. Retrieved June 22, 2020.
- Kaspersky Lab's Global Research and Analysis Team. (2015, February). Equation Group: Questions and Answers. Retrieved December 21, 2015.
Frequently Asked Questions
What is T1564.005 (Hidden File System)?
T1564.005 is a MITRE ATT&CK technique named 'Hidden File System'. It belongs to the Stealth tactic(s). 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...
How can T1564.005 be detected?
Detection of T1564.005 (Hidden File System) typically involves monitoring system logs, network traffic, and endpoint telemetry. Use SIEM rules, EDR solutions, and behavioral analytics to identify suspicious activity associated with this technique.
What mitigations exist for T1564.005?
Follow defense-in-depth principles including network segmentation, least privilege access, security monitoring, and regular patching to reduce the risk of this technique.
Which threat groups use T1564.005?
Known threat groups using T1564.005 include: Equation, Strider.