All files contains a main stream called $DATA. This stores the regular file contents
Additional streams can be created for hiding additional data (Even binary data like image can be added into a stream)
When viewing the size of the file the size of the alternative streams are not included
Streams can be attached to folders as well

:: Check if Alternate streams are present
dir /R
 
:: Create a new stream
echo [text] > file_name:stream_name
 
:: Read the data from the stream
more < file_name:stream_name
notepad file_name:stream_name

When we download files from the net the file is marked as untrusted as it is from somewhere else
The OS knows this because of an Alternative File Stream called Zone Identifier
This store the information about the zone of the file.

ZoneLocation
0My Computer
1Local Intranet Zone
2Trusted Sites Zone
3Internet Zone
4Restricted Sites Zone