Back in 2006 Google started providing alerts to users in order to warn them before they visited a site that distributed badware. In November of that year, Webmaster Tools (a.k.a. Google Sitemaps) started providing badware alerts to webmasters whose sites had been flagged.
Now Google has increased the information provided to webmasters fighting badware on their sites. The latest update of Webmaster Tools includes example URLs that have been determined to be dangerous. This helps webmasters locate hard-to-find malicious content such as 1-pixel iFrame inserts that prompt automatic download of malware from another site.