NTFS Alternate Data Streams

This article is going to explain NTFS Alternate Data Streams: what they are, where they are, how you can detect them, create them and how they are used by hackers. In short, NTFS Alternate Data Streams can be used by hackers to fork file data into existing files without altering the existing file’s function or size. You can guess where this is going, right ? They make it relatively easy to hide malicious code inside them which is much harder to detect.

Creating NTFS Alternate Data Streams is not complicated at all. You can use the “type” command to do that. To fork the file virus.exe into calc.exe you would use the command type virus.exe > calc.exe:virus:exe if they are in the same directory. Add the path if they are not. The size of the calculator does not change, the only indicator is that the file changed stamp is altered.

But executing those files must be harder, right ? Wrong again. To execute virus.exe you use the command “start”, in our example it would be start calc.exe:virus:exe.

A software like Stream Explorer can find those NTFS Alternate Data Streams on your hard drive. An alternative is List Alternate Data Streams

Related Articles:

Author: Martin Brinkmann, Thursday January 24, 2008 -
Tags:Alternate Data Streams, hacker, Hacking, malicious, ntfs, virus

Responses so far:

1. itoleck says:

   January 25, 2008 at 5:20 am

   You can also use the TechNet Sysinternals streams application. Here is the link.
   http://www.microsoft.com/technet/sysinternals/FileAndDisk/Streams.mspx

   Reply
2. Joe Whitehead says:

   January 26, 2008 at 11:24 pm

   New url for Sysinternals Streams:
   http://technet.microsoft.com/en-us/sysinternals/bb897440.aspx

   Those dummies keep changing the links and don’t redirect. :/

   Reply