Google also accused that Microsoft carries this secret practice through their Internet Explorer 8 and the Bing toolbar. Both these Microsoft products send user data to their mother company to identify how people use Google.
Google’s head of the blog Search Engine Land, Danny Sullivan, revealed the the company had conducted a “sting operation” to identify Bing’s malpractice. He claimed that through their operation, they found Bing search engine is keenly watching Google’s search result.
Deniying the Google’s charges, Stefan Weitz, director of Bing, told SearchEngineLand,
“As you might imagine, we use multiple signals and approaches when we think about ranking, but like the rest of the players in this industry, we’re not going to go deep and detailed in how we do it.” [source]