Google accused Microsoft on Tuesday of copying its search results for use in Microsoft's Bing, then the two companies bickered about it on stage at a San Francisco search conference.
Google, the dominant search engine, said Microsoft is using Internet Explorer 8 features to track what Google users are searching for, then copying those search results on its own search engine.
The Mountain View, Calif., company went so far as to conduct a "sting" operation, manually planting search results for gibberish terms. Those same results later showed up in Bing search results for the same gibberish.
On a company blog, Google said it wants Microsoft to stop the practice.
Microsoft acknowledged it uses IE8 and a Bing toolbar to track user information but said it's just one factor in determining Bing search results. Harry Shum, a corporate vice president for search at Microsoft, referred to Google's sting as a "spy-novelesque stunt."
The allegations were first reported Tuesday by the site SearchEngineLand.com. Later, Shum and Google principal engineer Matt Cutts argued over them on stage Tuesday at the Farsight 2011 conference in San Francisco. Their appearance, for a scheduled discussion on the future of search, was webcast.
The tiff underscores how competitive juices still run strong in search, which Google dominates with a 66.6 percent share of the U.S. market in December, according to comScore. By contrast, Microsoft had 12 percent and Yahoo, whose search engine Microsoft now runs, had 16 percent.
In the Farsight discussion, Cutts explained how Google determined Microsoft used the Bing toolbar and an IE8 "suggested sites" feature to track searches done on Google, then copy those results in Bing.
He confirmed that Google inserted fake search results on certain terms only to find them later on Bing.
"It's almost like a mapmaker that inserts a fake street and sees if that street gets copied or if a Yellow Pages inserts a fake number," Cutts said.
Shum did not deny that the Bing toolbar or IE8 features track data, adding that all search operations track customer behavior.
"We learn from our customers," Shum said.
"We have been very clear we use customer data. My understanding is other search engines also use a similar thing."
Cutts countered, "I'm not sure users realize that by installing the Bing bar or installing suggested sites on IE8 that those results are encrypted and sent to Microsoft."
Shum then criticized Google about online spam, saying, "I think Google, as an industry leader, would be responsible for a lot of spam we receive."
Google has been hit with privacy complaints that it tracks what people search for. By saying Microsoft is using its browser tools to track users, Google appeared to be trying to paint Microsoft and Bing with the same brush.
On Tuesday, Google issued a statement from Amit Singhal, a Google fellow:
"At Google we strongly believe in innovation and are proud of our search quality. We look forward to competing with genuinely new search algorithms out there, from Bing and others — algorithms built on core innovation, and not on recycled search results copied from a competitor."
Microsoft also posted a blog item, from Shum, that said: "To be clear, we learn from all of our customers. What we saw in today's story was a spy-novelesque stunt to generate extreme outliers in tail query ranking. It was a creative tactic by a competitor, and we'll take it as a backhanded compliment. But it doesn't accurately portray how we use opt-in customer data as one of many inputs to help improve our user experience."