"For months, investigators at Microsoft Corp. MSFT +0.95% hunkered down in front of their computer monitors, patiently stalking the shadowy figures behind what the company says is a major Web ad-fraud machine.
Then, on Thursday, they pounced. Armed with a court order and law enforcement help overseas, the team took steps to cut off communication links to European-based servers considered the mega-brain for an army of zombie computers known as ZeroAccess."