LAS VEGAS (AP) — Against a backdrop of cyberattacks that have grown into full-fledged sabotage, Facebook chief security officer Alex Stamos brought a sobering message Wednesday to hackers and security experts at the Black Hat conference.

In short: it's time for hackers once known for relatively harmless mischief to shoulder responsibility for helping detect and prevent major attacks that threaten billions of internet users around the world.

The Black Hat security gathering, happening this week in Las Vegas, follows a series of attacks and data breaches that have paralyzed hospitals, disrupted...