From Robert Lemos’ “Bot-infected PCs get a refresh” (SecurityFocus: 28 December 2006):
On Christmas day, the number of bots tracked by the Shadowserver group dropped nearly 20 percent.
The dramatic decrease in weekly totals–from more than 500,000 infected systems to less than 400,000 computers–puzzled researchers. The Internet Storm Center, a threat monitoring group managed by the SANS Institute, confirmed a drop of about 10 percent.
One of the Internet Storm Center’s network monitoring volunteers posited that the decrease was due to the large number of computers given as gifts this Christmas. The systems running Microsoft Windows XP will be using Service Pack 2, which also means the firewall will be on by default, adding an additional hurdle for bot herder looking to reclaim their drones.
“Many of the infected machines are turned off, the new shiny ones have not been infected, and the Internet is momentarily a safer place,” Marcus Sachs, director of the ISC, stated in a diary entry. “But like you said, give it a few weeks and we’ll be right back to where we started from.”