"The new Malware Search engine provides a Web interface that allows
anyone to enter the name of a known virus or Trojan and find Google
results for Web sites hosting malicious executables.
The release of the search engine was motivated in part by a recent announcement by Websense Security Labs, of San Diego-based Websense, that it was using the freely available Google SOAP (Simple Object Access Protocol) Search API to find dangerous .exe files sitting on Web servers." - eWeek
In a nutshell, a web app wrapper to the google SOAP API which exposes additional search functionality.
Article Link: http://www.eweek.com/article2/0,1895,1990158,00.asp