Users can search again, learn more about malicious code at the site StopBadware.org or proceed to the suspect site anyhow - at their own risk, of course.
Google Inc. said its initiative is just starting and is by no means comprehensive.
"To begin we'll only be identifying a small number of sites, but we'll be expanding our coverage over time," the company said in a statement. "Finding new and better ways to protect our users is a perpetual project, and we'll continue to work hard in this area."
Google is one of the main sponsors of StopBadware.org, a project that researchers from Harvard and Oxford universities are hoping to turn into a clearinghouse for information on spyware and other malicious software.
So far, StopBadware has identified only one site as malicious, and efforts to reach that site from Google worked normally Wednesday.
But Google has identified other sites as problems and is offering warnings for those. The company said the sites have been identified using software algorithms and verified with outside experts.
Jonathan Zittrain, a Harvard and Oxford professor involved with StopBadware, said the project may one day release lists of suspect sites still under investigation, but would most likely do so for everyone and not just sponsors like Google.
By Anick Jesdanun