Beu reports in a Search Engine Watch Forums thread that Google has updated their Webmaster Guidelines again. This time, they added a link to types malicious behavior that is against Google's guidelines.
Don't create pages that install viruses, trojans, or other badware.
Don't create pages with malicious behavior, such as phishing or installing viruses, trojans, or other badware.
The link takes you to a page on Installing viruses and other badware.
Frank, AussieWebmaster comments saying, "you figure that would be understood by now." But in reality, you would think that way about most of Google's Webmaster Guidelines. Google can't win on that front, I'll give it to Google on that one.
Forum discussion at Search Engine Watch Forums.
Update From Matt Cutts of Google: Just want to highlight a comment from Matt on this entry:
I wanted us to be crystal clear that we may remove phishing urls as well.