Ask HN: How can I learn to be a cyber security expert?

I've become increasingly disturbed by high profile hacks and data breaches. Maybe I'm wrong, but it looks like these things are getting worse — and when there's a data breach, hack, or privacy violation — the most vulnerable people are hit hardest. I'm a web dev, thinking about focusing on helping people stay secure online. What are your tips for becoming a cyber security expert? How can I start learning online?