Alternate Data Streams

Creating a benign text file:
echo "this is benign" > benign.txt
Get-ChildItem
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Hiding an evil.txt file inside the benign.txt
cmd '/c echo "this is evil" > benign.txt:evil.txt'
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Note how the evil.txt file is not visible through the explorer - that is because it is in the alternate data stream now. Opening the benign.txt shows no signs of evil.txt. However, the data from evil.txt can still be accessed as shown below in the commandline - type benign.txt:evil.txt:
Additionally, we can view the data in the notepad as well by issuing:
notepad .\benign.txt:evil.txt

Note that powershell can also help finding alternate data streams:
Get-Item c:\experiment\evil.txt -Stream *
Get-Content .\benign.txt -Stream evil.txt

Hide Artifacts: NTFS File Attributes, Sub-technique T1564.004 - Enterprise | MITRE ATT&CK®
https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.core/providers/filesystem-provider/get-item-for-filesystem?view=powershell-6
docs.microsoft.com
Introduction to Alternate Data Streams
Malwarebytes Labs
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