In fact, we found the answer by searching through our archives on late Twentieth-century computing technology. Geordi presses a key, and a logo appears on the computer screen. Riker looks puzzled.
Data turns to answer.
Once inside their root command unit, it will begin consuming system resources at an unstoppable rate. The use of resources increases exponentially with each iteration. The Borg will not be able to adapt quickly enough. Eventually all of their processing ability will be taken over and none will be available for their normal operational functions. Apparently the Borg have circumvented that part of the plan by not sending in their registration cards.