Security: Preserve ADS Zone Info When Recovering Files
Posted: Sun May 21, 2017 4:06 pm
For each downloaded file, Windows adds some zone information in an NTFS alternate data stream (ADS).
This "Zone.Identifier" information is used for showing warnings about running files downloaded from the Internet
and is also used by Windows Smart Screen to trigger a check of the reputation of downloaded executable files.
When files are recovered from a sandbox, this zone info is lost (i.e. the NTFS alternate data stream is not preserved).
This causes Smart Screen not to check the downloaded file, as it needs the zone info as a trigger.
It would be nice (security-wise) if the ADS info could be preserved for files recovered from a sandbox.
Steps to reproduce:
1) Run a browser (I used Firefox) in a sandbox
2) Go to https://demo.smartscreen.msft.net/
3) Download either the "Unknown program" or "Known Malware" app rep demo files at the bottom of the page.
3) Recover the downloaded file from the sandbox
4) Double-click the downloaded file in Explorer
5) Windows Smart Screen will NOT show any warnings. (The ADS zone info has been lost during the recovery process)
Compare:
1) DISABLE Sandboxie, run Browser unsandboxed
2) Go to https://demo.smartscreen.msft.net/
3) Download either the "Unknown program" or "Known Malware" app rep demo files at the bottom of the page.
4) Double-click the downloaded file in Explorer
5) Windows Smart Screen will show the proper warnings. (The ADS zone info is left untouched)
PS: This utility can be used for listing the ADS: http://www.nirsoft.net/utils/alternate_ ... reams.html
This "Zone.Identifier" information is used for showing warnings about running files downloaded from the Internet
and is also used by Windows Smart Screen to trigger a check of the reputation of downloaded executable files.
When files are recovered from a sandbox, this zone info is lost (i.e. the NTFS alternate data stream is not preserved).
This causes Smart Screen not to check the downloaded file, as it needs the zone info as a trigger.
It would be nice (security-wise) if the ADS info could be preserved for files recovered from a sandbox.
Steps to reproduce:
1) Run a browser (I used Firefox) in a sandbox
2) Go to https://demo.smartscreen.msft.net/
3) Download either the "Unknown program" or "Known Malware" app rep demo files at the bottom of the page.
3) Recover the downloaded file from the sandbox
4) Double-click the downloaded file in Explorer
5) Windows Smart Screen will NOT show any warnings. (The ADS zone info has been lost during the recovery process)
Compare:
1) DISABLE Sandboxie, run Browser unsandboxed
2) Go to https://demo.smartscreen.msft.net/
3) Download either the "Unknown program" or "Known Malware" app rep demo files at the bottom of the page.
4) Double-click the downloaded file in Explorer
5) Windows Smart Screen will show the proper warnings. (The ADS zone info is left untouched)
PS: This utility can be used for listing the ADS: http://www.nirsoft.net/utils/alternate_ ... reams.html