Here's another link talking about this in detail.
This is confirmed by correspondence 14-15 January 2009 between Mr. Geoffrey Walter Ritchey and NIST:
I respectfully request copies of the following NIST records:
Instructions for running the NIST simulation of the collapse of World Trade Center Building 7 on my own hardware including required software, required
hardware, and any parameters to the program. ...
Geoffrey Walter Ritchey
The response from UNITED STATES DEPARTMENT OF COMMERCE National Institute of Standards and Technology was simple:
NIST has no documents that are responsive to your request.
Structural Analysis Input used for the Damage Analysis made secret!!
FINDING REGARDING PUBLIC SAFETY INFORMATION
Pursuant to Section 7(d) of the National Construction Safety Team Act, I hereby find that the disclosure of the information described below, received
by the National Institute of Standards and Technology ("NIST"), in connection with its investigation of the technical causes of the collapse of the
World Trade Center Towers and World Trade Center Building 7 on September 11,2001, might jeopardize public safety. Therefore, NIST shall not release
the following information:
1. All input and results files of the ANSYS 16-story collapse initiation model with detailed connection models that were used to analyze the
structural response to thermal loads, break element source code, ANSYS script files for the break elements, custom executable ANSYS file, and all
Excel spreadsheets and other supporting calculations used to develop floor connection failure modes and capacities.
2. All input files with connection material properties and all results files of the LS-DYNA 47-story global collapse model that were used to simulate
sequential structural failures leading to collapse, and all Excel spreadsheets and other supporting calculations used to develop floor connection
failure modes and capacities.
Patrick Gallagher Director National Institute of Standards and Technology
Dated: JUL 09 2009
(Note - the date should probably be JUL 09 2010 as Gallagher was not with NIST JUL 2009!)