Was a high-profile hedge-fund arrest over the weekend just the first domino to fall? Bloomberg reports that the Feds are preparing to file charges against “a wider array of insider-trading networks”—some of which are connected to the hedge-fund manager Raj Rajaratnam, who was arrested on Friday in the biggest insider-trading case in decades. The crackdown is based on at least two years of investigation, and targets hedge-fund managers, lawyers, and other Wall Street figures. It relies on wiretaps and an SEC data-mining program that pinpoints similar well-timed investments—signs that the Feds are targeting insider traders with more aggressive tactics. Rajaratnam, the founder of the Galleon Group, stands accused of reaping $18 million based on tips from a hedge fund, a credit-rating firm, and employees at companies like Intel and IBM.