As a red team member, having a variety of tools and techniques at your disposal is essential for achieving your objectives. One technique that can be extremely useful for red teams is the ability to hide data on a Windows NTFS file system using alternate data streams. This technique can conceal sensitive information from network defenders and blue teams. In this article, we will explore what alternate data streams are, how they can be used to hide data, some examples of their use, and how to detect them.
What are Alternate Data Streams?
Alternate data streams (ADS) are a feature of the Windows NTFS file system that allows additional data to be attached to a file without changing the file’s primary data stream. This feature was originally intended to support compatibility with the Macintosh Hierarchical File System (HFS), which also allowed for alternate data streams. However, this feature has since been used for other purposes, including hiding data from prying eyes.
How to Hide Data Using Alternate Data Streams
Hiding data using alternate data streams can be accomplished using built-in Windows tools or third-party software. The simplest way to create an alternate data stream is to use the command line utility, “type”. To do this, the user would first create the file with the data they want to hide. Then, they would use the “type” command to append the hidden data to the end of the file, separated by a special character sequence, such as “::”.
For example, to hide a password in a file called “example.txt”, the user could use the following command:
type password.txt >> example.txt:hidden.txt
This would append the contents of “password.txt” to the end of “example.txt” and save it in the alternate data stream called “hidden.txt”.
Another example is to hide data in an image file. The user could use a tool like “Steghide” to embed a message or file into the image file’s alternate data stream. This would allow the user to conceal the message or file within the image, making it difficult to detect.
Detecting Alternate Data Streams
Detecting alternate data streams can be challenging, as they are not visible in Windows Explorer or other file managers. However, there are several tools and techniques that can be used to detect alternate data streams.
One way to detect alternate data streams is to use the command line utility, “dir”, with the “/r” flag. This will display any alternate data streams that are associated with a file. For example, to display the alternate data streams associated with a file called “example.txt”, the user could use the following command:
dir /r example.txt
Another tool that can be used to detect alternate data streams is “Streams”. This is a command line utility that can be used to display and manipulate alternate data streams. The user can use the “Streams” command to display the alternate data streams associated with a file, and then use other tools to extract or analyze the data.
Implications of Using Alternate Data Streams to Hide Data
While using alternate data streams to hide data can be an effective way to keep sensitive information hidden from prying eyes, there are several implications that should be considered before using this technique. One of the main implications is that this technique may be illegal in some jurisdictions, as it can be used to hide illegal content, such as child pornography or stolen intellectual property. Additionally, using alternate data streams to hide data can be considered a violation of user trust and may be a breach of ethical standards.
Another implication of using alternate data streams to hide data is that it may not be as secure as it seems. While alternate data streams can be effective at hiding data from casual users, they may not be able to withstand a determined attacker. A knowledgeable attacker may be able to detect the presence of an alternate data stream on a file and extract the hidden data. Additionally, the use of alternate data streams to hide data may be detected by anti-virus software, which can lead to false positives and may alert network defenders to the presence of suspicious activity.
Conclusion
The ability to hide data on a Windows NTFS file system using alternate data streams is a valuable technique that can be used by red teams to conceal sensitive information from prying eyes. While this technique may be effective in some scenarios, it is important to consider the implications before using it. This technique may be illegal in some jurisdictions and may be a breach of ethical standards. Additionally, the use of alternate data streams to hide data may not be as secure as it seems and may be detected by anti-virus software or a determined attacker. As with any technique, it’s important to weigh the risks and benefits before using it.