5.1 NTFS Streams
All files on an NTFS volume consist of at least one stream - the main stream – this is the normal, viewable file in which data is stored. The full name of a stream is of the form below.
<filename>:<stream name>:<stream type>
The default data stream has no name. That is, the fully qualified name for the default stream for a file called "sample.txt" is "sample.txt::$DATA" since "sample.txt" is the name of the file and "$DATA" is the stream type.
A user can create a named stream in a file and "$DATA" as a legal name. That means that for this stream, the full name is sample.txt:$DATA:$DATA. If the user had created a named stream of name "bar", its full name would be sample.txt:bar:$DATA. Any legal characters for a file name are legal for the stream name (including spaces). For more information about the naming format for streams, see [MS-FSCC]. For more information about the attributes of a stream, see [MS-FSA].
In the case of directories, there is no default data stream, but there is a default directory stream. Directories are the stream type $INDEX_ALLOCATION. The default stream name for the type $INDEX_ALLOCATION (a directory stream) is $I30. (This contrasts with the default stream name for a $DATA stream, which has an empty stream name.) The following are equivalent:
Although directories do not have a default data stream, they can have named data streams. These alternate data streams are not normally visible, but can be observed from a command line using the /R option of the DIR command.