A stranger in your hotel room? Kitty-litter shortages? Online attacks are causing real-world effects.

It was past midnight when Alessandra Millican and a friend entered the Bellagio hotel room that was costing them hundreds of dollars a night, but unexpected noises made them stop cold.

“We started hearing grunts,” she said. “It’s somebody waking up — we were halfway through the room and we realized there’s somebody sleeping in here.”

Millican…