CodeRed gets smarter...
New Worm More Virulent 

 Security experts say a virulent new worm dubbed "Code Red II" installs a back door to give hackers quick access to

 Each of the infected systems attacks 300 other computers, making the new worm more virulent than Code
 Red, experts say. Where Code Red simply attacked random Web servers, Code Red II seeks out clusters of
 nearby systems, knowing that pockets of Internet addresses will often use the same software.

Birds of a feather flock together, and so do Servers running the same OS.

CodeRed used a 'random attack', whereas this worm[Code Red II] knows more about the network it is attacking and is focusing on nodes that are probably vulnerable to infection... scary.