Microsoft is now accusing Google of using a form of click fraud to set up its Bing Sting, a stunt unveiled by the search giant at the Farsight 2011 tech conference in Silicon Valley.

Google on Tuesday grabbed headlines in the tech press by disclosing an FBI-like sting operation purporting to produce evidence that Bing is intentionally and systematically copying Google search results.

Today, Yusuf Mehdi, senior vice president for Microsoft's Online Services Division, fired back. Mehdi says Google's sting, in fact, was "rigged to manipulate Bing search results" through the use of click fraud -- the elaborate trickery scammers use to fake clicks on Web ads in order to get paid by advertisers.

"What does all this cloak-and-dagger click fraud prove?" asks Mehdi. "Nothing anyone in the industry doesn't already know."

Google senior engineer Amit Singhal told Technology Live that the search giant stands by its original allegations that Bing is a copy cat.

"At Google we strongly believe in innovation," says Singhal. "We look forward to competing with genuinely new search algorithm built on core innovation, and not on recycled search results copied from a competitor."

In an exclusive Technology Live interview, Bing Director Stefan Weitz elaborated on why Microsoft contends Google is the real cheater in this confrontation:

TL: So Google really blindsided you with this?

Weitz: It was a surprise, not so much the stunt itself. I was more surprised by the fact that it isn't intellectually honest. It's just not true.

TL: So what was manipulated?

Weitz: What Google did was clever, I'll give them that. They basically took a bunch of nonsensical words, like xlgr493, and then modified their own algorithm to point the search query for that particular word to a real site. So xlgr493 refers to kittycat.com.

Then about 20 of them went to their houses at night, and, probably over a glass of merlot, started using the Bing toolbar to query Google for that particular nonsensical word. Then the next day they showed that if you searched for that nonsensical word on Bing, the faked site would appear as the first result.

TL: And the first Bing result would be the same as the first Google result for the same nonsensical word?

Weitz: Yes. Google's engineers basically issued a bunch of queries to Google from the Bing toolbar for that nonsensical word. They already had tuned the Google search engine to display a certain link when it saw that nonsensical word. By using the Bing toolbar, and then clicking on that link, the data flowed through normal processes back to Microsoft as it should. From there the data gets analyzed against a thousand different signals, one of which is our ranker. There is no copying here at all.

TL: So the sting was set up knowing only your ranking signal would trigger, not any of the others?

Weitz: There were no other signals, nothing else to look up. They artificially created this association, and there was nothing else we could use to figure out what the user was asking for. So we pulled that one signal, which was the faked one from Google.

TL: Do you take this as evidence that Google will get more down and dirty about defending its turf now that Larry Page is replacing Eric Schmidt as CEO?

Weitz: At the end of the day, we're all a bunch of geeks competing, right. Everyone's competing hard and that's actually good for the users because, in the end, they get a great product.