Updated in 17 Feb,2025..
Ever downloaded a Word document or PowerPoint presentation and noticed it says "Trust this file to edit"?
That happens because Windows tags downloaded files with something called a Zone.Identifier. This tag helps the system figure out if a file came from the Internet, and in some cases, even where it came from.
Pretty cool, right?
What Is Zone.Identifier and How Does It Work?
Windows has been using the Zone.Identifier tag since Windows XP SP2. Whenever you download a file from the Internet to an NTFS drive, an alternate data stream (ADS) gets added to it. This extra data doesn’t change the file itself but contains useful information about its origin.
Most web browsers (like Chrome, Edge, and Firefox) and apps like email clients automatically tag files this way. This process is known as "Mark of the Web" (MotW). It uses the Windows API function IAttachmentExecute to make sure files are handled safely.
However, there are some exceptions—Internet Explorer, for example, only tags certain file types, and PowerShell or FTP downloads often don’t get tagged at all.
What’s Inside a Zone.Identifier?
If you inspect a Zone.Identifier ADS using a tool like FTK Imager, you’ll see details like:
ZoneID – A number indicating the security zone the file came from. Here are the possible values:
0 – My Computer (local files)
1 – Intranet (internal network)
2 – Trusted sites
3 – Internet (most web downloads)
4 – Untrusted (flagged as risky by Microsoft SmartScreen)
ReferrerURL – The website the file was downloaded from (if available)
HostURL – The direct download link (if available)
Not all browsers store ReferrerURL or HostURL, especially in private browsing modes.
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Example :
Analyzing Zone.Identifier ADS:
By analyzing the presence of Zone.Identifier ADS, forensic analysts can identify potentially malicious files that were downloaded from the internet.
**This analysis is particularly useful when examining critical system directories like C:\Windows\System32, where the presence of ZoneID=3 can raise red flags.**
Applications in Forensic Investigations:
ADS analysis, especially focusing on Zone.Identifier streams, can provide valuable insights into the origins of files, aiding forensic investigations in various scenarios, including malware analysis, digital forensics, and e-discovery.
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Update Made on January 2025
I want to introduce you to one of the best tools I always use, which is also a part of the KAPE toolkit.
The tool is called MFTECmd.exe.
This tool parses key artifacts such as $MFT, $J, $Boot, $SDS, and $I30 and provides the output in a CSV format.
I haven’t written an article about this tool yet, but I plan to do so soon.
Now, you might be wondering why I’m telling you about this tool. Let me explain.
Here’s an example: Suppose you’ve parsed an $MFT file using MFTECmd.exe, and you have a file on the device. Now, the client wants to know how this file ended up on the system.
Did the user download it? If so, from which link?
If you’ve used MFTECmd.exe, you don’t need to worry. Simply open the output in Timeline Explorer, navigate to the Zone ID Contents column, and check the information.
As shown in the screenshot below, Zone ID 3 indicates the file was downloaded from the internet. Moreover, the URL is also mentioned in the output.
See how easy and efficient it is to gather this information!
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How Attackers Exploit Alternate Data Streams
Hackers and red-team testers love alternate data streams because they allow them to hide files in plain sight.
For example, instead of storing malware as a regular .exe file, they can embed it inside an ADS attached to a harmless-looking text file.
A common attack trick is running a malicious DLL stored in an ADS using rundll32.exe. Standard file listing tools won’t even see the hidden ADS, making it much harder for security tools to detect the malware.
How You Can Spot and Investigate ADS
Thankfully, there are ways to uncover these hidden streams:
Use CMD: Run dir /r to list all data streams attached to files.
Use PowerShell: Run Get-Item * -Stream * to find hidden ADS in a folder.
Use forensic tools: Software like istat and icat can dig even deeper into ADS details.
One place you’ll always find a ton of alternate data streams is the Downloads folder since every file you grab from the Internet gets tagged with a Zone.Identifier.
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Why This Matters
A huge number of security breaches start with a simple file download. Understanding how Windows tracks downloaded files can help spot suspicious activity early. If you see a weird-looking program in C:\Windows\System32 with a Zone.Identifier tag, you know something’s off.
By knowing how to check for alternate data streams, you can catch hidden threats and stay one step ahead of attackers.
----------------------------------------------Dean---------------------------------------------------
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