The British computer expert whose research was linked to the weekend’s damaging Internet attack pledged Wednesday to reconsider publishing blueprints for attack programs that exploit flaws he discovers in popular software. Leading researchers have concluded that the software in Saturday’s attacks was modified by unknown hackers from blueprints published months earlier by David Litchfield of NGS Software Ltd. The virus-like attack slowed e-mail and Web surfing — and even shut down ATM operations for hours at some large banks. Litchfield last year identified the flaw in database software from Microsoft Corp. that left at least 1 million computers susceptible to break-ins and infections. His company also developed a program protecting users. Full Story