Coding Horror has written an informative article on Rainbow Tables, and why Windows servers can be particularly vulnerable.
The multi-platform password cracker Ophcrack is incredibly fast. How fast? It can crack the password “Fgpyyih804423″ in 160 seconds. Most people would consider that password fairly secure. The Microsoft password strength checker rates it “strong”. The Geekwisdom password strength meter rates it “mediocre”.
Why is Ophcrack so fast? Because it uses Rainbow Tables. No, not the kind of rainbows I have as my desktop background.