Атрибуты файла NTFS
Every New Technology File System (NTFS) formatted partition contains a Master File Table (MFT) that maintains a record for every file/directory on the partition. (Citation: SpectorOps Host-Based Jul 2017) Within MFT entries are file attributes, (Citation: Microsoft NTFS File Attributes Aug 2010) such as Extended Attributes (EA) and Data [known as Alternate Data Streams (ADSs) when more than one Data attribute is present], that can be used to store arbitrary data (and even complete files). (Citation: SpectorOps Host-Based Jul 2017) (Citation: Microsoft File Streams) (Citation: MalwareBytes ADS July 2015) (Citation: Microsoft ADS Mar 2014) Adversaries may store malicious data or binaries in file attribute metadata instead of directly in files. This may be done to evade some defenses, such as static indicator scanning tools and anti-virus. (Citation: Journey into IR ZeroAccess NTFS EA) (Citation: MalwareBytes ADS July 2015)
Контрмеры |
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| Контрмера | Описание |
|---|---|
| NTFS File Attributes Mitigation |
It may be difficult or inadvisable to block access to EA and ADSs. (Citation: Microsoft ADS Mar 2014) (Citation: Symantec ADS May 2009) Efforts should be focused on preventing potentially malicious software from running. Identify and block potentially malicious software that may contain functionality to hide information in EA and ADSs by using whitelisting (Citation: Beechey 2010) tools like AppLocker (Citation: Windows Commands JPCERT) (Citation: NSA MS AppLocker) or Software Restriction Policies (Citation: Corio 2008) where appropriate. (Citation: TechNet Applocker vs SRP) Consider adjusting read and write permissions for NTFS EA, though this should be tested to ensure routine OS operations are not impeded. (Citation: InsiderThreat NTFS EA Oct 2017) |
| Restrict File and Directory Permissions |
Restrict access by setting directory and file permissions that are not specific to users or privileged accounts. |
Обнаружение
Forensic techniques exist to identify information stored in NTFS EA. (Citation: Journey into IR ZeroAccess NTFS EA) Monitor calls to the ZwSetEaFile and ZwQueryEaFile Windows API functions as well as binaries used to interact with EA, (Citation: Oddvar Moe ADS1 Jan 2018) (Citation: Oddvar Moe ADS2 Apr 2018) and consider regularly scanning for the presence of modified information. (Citation: SpectorOps Host-Based Jul 2017)
There are many ways to create and interact with ADSs using Windows utilities. Monitor for operations (execution, copies, etc.) with file names that contain colons. This syntax (ex: file.ext:ads[.ext]) is commonly associated with ADSs. (Citation: Microsoft ADS Mar 2014) (Citation: Oddvar Moe ADS1 Jan 2018) (Citation: Oddvar Moe ADS2 Apr 2018) For a more exhaustive list of utilities that can be used to execute and create ADSs, see https://gist.github.com/api0cradle/cdd2d0d0ec9abb686f0e89306e277b8f.
The Streams tool of Sysinternals can be used to uncover files with ADSs. The dir /r command can also be used to display ADSs. (Citation: Symantec ADS May 2009) Many PowerShell commands (such as Get-Item, Set-Item, Remove-Item, and Get-ChildItem) can also accept a -stream parameter to interact with ADSs. (Citation: MalwareBytes ADS July 2015) (Citation: Microsoft ADS Mar 2014)
Ссылки
- Pravs. (2009, May 25). What you need to know about alternate data streams in windows? Is your Data secure? Can you restore that?. Retrieved March 21, 2018.
- Moe, O. (2018, April 11). Putting Data in Alternate Data Streams and How to Execute It - Part 2. Retrieved June 30, 2018.
- Moe, O. (2018, January 14). Putting Data in Alternate Data Streams and How to Execute It. Retrieved June 30, 2018.
- Harrell, C. (2012, December 11). Extracting ZeroAccess from NTFS Extended Attributes. Retrieved June 3, 2016.
- Marlin, J. (2013, March 24). Alternate Data Streams in NTFS. Retrieved March 21, 2018.
- Arntz, P. (2015, July 22). Introduction to Alternate Data Streams. Retrieved March 21, 2018.
- Microsoft. (n.d.). File Streams. Retrieved December 2, 2014.
- Hughes, J. (2010, August 25). NTFS File Attributes. Retrieved March 21, 2018.
- Atkinson, J. (2017, July 18). Host-based Threat Modeling & Indicator Design. Retrieved March 21, 2018.
- Sander, J. (2017, October 12). Attack Step 3: Persistence with NTFS Extended Attributes – File System Attacks. Retrieved March 21, 2018.
Связанные риски
Каталоги
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