Like many files of its kind (similar to smile.jpg or Mereana Mordegard Glesgorv ), 21372.mp4 developed a reputation for being Rumors spread that:
In many early video hosting scripts, files were assigned sequential ID numbers. "2137" or "21372" might simply have been the ID of a corrupted upload that became a blank canvas for people to project scary stories onto.
The file contained "encoded data" that could bypass firewalls.
Watching the full video would cause the viewer’s computer to crash or lead to a "blue screen of death."