More than 120,000 Windows-based computers running Internet Explorer 9 are infected in the U.S., researchers say.
Microsoft has launched a stinging attack on Google over accusations that Bing copies Google's search results.
As part of a class-action settlement, Yahoo plans to create a new ad distribution option that will give advertisers more control over where ads purchased through Yahoo appear.
Click Forensics concludes that bogus clicks on online advertisements rose to 17.1 percent for the fourth quarter, driven increasingly by botnets.
Bogus clicks on ads, which can make money for Web sites but cost advertisers, were no more common in the second quarter. But click fraud is getting more sophisticated.
The click-fraud auditor says it built software in partnership with Yahoo that lets advertisers automatically deal with the costs of fraudulent clicks in a search ad campaign.
A plaintiff-only firm that has successfully gone after Yahoo and Google in the past says Citysearch is "encouraging" click fraud.
A study finds that click fraud rates for online advertising dropped slightly from the last quarter of 2007 to the first of 2008.
The industry-first partnership gives Yahoo a way to distinguish itself from Google.
Report says click fraud rate is up due to increased use of botnets to automate the clicking on ads.