Alternate Data Streams (ADS) in Windows

Alternate Data Streams (ADS) is a relatively obscure but powerful feature in the Windows file system. ADS allows you to attach hidden streams of data to files and folders. This can be useful for various purposes, including adding metadata, custom icons, or even hiding malicious data. In this article, we'll explore how to create and manage ADS.

Creating an Alternate Data Stream

Creating an ADS is relatively straightforward, and you can do it using the type command or PowerShell. To create an ADS, follow these steps:

Using the type Command

1. Open Command Prompt.

2. Use the type command to create an ADS. The syntax is as follows:

type [data] > [file]:[stream]

• [data]: The data you want to add to the stream.
• [file]: The path to the target file.
• [stream]: The name of the alternate data stream (without spaces).

For example, to create an ADS named "hidden_info" for a file named "document.txt" with the content "This is a hidden stream of data," you would use:

type "This is a hidden stream of data" > document.txt:hidden_info

Using PowerShell

1. Open PowerShell.

2. To create an ADS, you can use the Add-Content cmdlet. The syntax is as follows:

Add-Content -Path [file] -Value [data] -Stream [stream]

• [file]: The path to the target file.
• [data]: The data you want to add to the stream.
• [stream]: The name of the alternate data stream (without spaces).

For example, to create the same "hidden_info" ADS for "document.txt," you would use:

Add-Content -Path document.txt -Value "This is a hidden stream of data" -Stream hidden_info

Viewing Alternate Data Streams

To view the ADS associated with a file, you can use the more command or PowerShell. Here's how:

Using the more Command

1. Open Command Prompt.

2. To view the content of an ADS, use the more command with the :stream syntax:

more < [file]:[stream]

For example, to view the content of the "hidden_info" ADS in "document.txt," you would use:

more < document.txt:hidden_info

Using PowerShell

1. Open PowerShell.

2. To view the content of an ADS, you can use the Get-Content cmdlet with the -Stream parameter:

Get-Content -Path [file] -Stream [stream]

For example, to view the content of the "hidden_info" ADS in "document.txt," you would use:

Get-Content -Path document.txt -Stream hidden_info

Conclusion

Alternate Data Streams provide a hidden and versatile way to store additional data associated with files and folders on Windows. While they have legitimate use cases, they can also be exploited for malicious purposes, so it's essential to be aware of their presence and use them responsibly.