New Technology File System (NTFS)
The New Technology File System (NTFS) is a file system developed and introduced by Microsoft in 1993 with Windows 3.1. As a replacement for the FAT file system, it quickly became the standard for Windows 2000, Windows XP and Windows Server 2003.
The features of NTFS include:
- Improved performance, reliability and disk space utilization
- Security access control lists
- File system journaling
Alternate Data Streams
The NTFS file system includes a feature referred to as Alternate Data Streams (ADSs). This feature has also been referred to as "multiple data streams", "alternative data streams", etc. ADSs were included in NTFS in order to support the resource forks employed by the Hierarchal File System (HFS) employed by Macintosh systems.
As of Windows XP SP2, files downloaded via Internet Explorer, Outlook, and Windows Messenger were automatically given specific "zoneid" ADSs. The Windows Explorer shell would then display a warning when the user attempted to execute these files (by double-clicking them).
Sysadmins should be aware that prior to Vista, there are no tools native to the Windows platform that would allow you to view the existence of arbitrary ADSs. While ADSs can be created and their contents executed or viewed, it wasn't until the "/r" switch was introduced with the "dir" command on Vista that arbitrary ADSs would be visible. Prior to this, tools such as LADS could be used to view the existence of these files.
Examiners should be aware that most forensic analysis applications, including EnCase and ProDiscover, will display ADSs found in acquired images in red.