n February, Iranian hackers took down the computer system of gambling magnate Sheldon Adelson’s casino empire, wiping hard drives clean and shutting down email. Las Vegas Sands, the world’s largest gaming company, was devastated by the attack. But until a Bloomberg Businessweek report Thursday night, the company had never revealed the extent of the hack. Coming months before the recent hack on Sony Pictures, the hit on Sands is now believed to be the first major destructive cyberattack on a U.S. business, although there are likely others that have gone unreported. From the instant the offensive started, Las Vegas Sands...