NTFS File Attributes
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.  Within MFT entries are file attributes,  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).    
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.  
It may be difficult or inadvisable to block access to EA and ADSs.   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  tools like AppLocker   or Software Restriction Policies  where appropriate. 
Consider adjusting read and write permissions for NTFS EA, though this should be tested to ensure routine OS operations are not impeded. 
Forensic techniques exist to identify information stored in NTFS EA.  Monitor calls to the ZwSetEaFile and ZwQueryEaFile Windows API functions as well as binaries used to interact with EA,   and consider regularly scanning for the presence of modified information. 
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.    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.  Many PowerShell commands (such as Get-Item, Set-Item, Remove-Item, and Get-ChildItem) can also accept a
-stream parameter to interact with ADSs.  
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