SAN FRANCISCO—Matt Cutts, in charge of weeding out malicious users on Google's sprawling network, provided people at the Web 2.0 Summit with some tips on how to avoid being taken down by hackers and other malcontents.

This is especially crucial in the age of proliferating Web services such as Facebook, Digg, MySpace.com and Twitter, which boast millions of users.

Cutts told a packed room here Nov. 5 that site admins need to put on their "black hats." In other words, to catch or thwart a spammer or hacker, an admin needs to think like one.

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The idea is to stop the spread of so-called "virtual blight," which can rot away valuable Web services.

Here are some slides from Cutts' presentation showing how companies can recognize this type of activity to protect themselves.