Most breaches don't come from exotic zero-days. They come from unpatched dependencies, misconfigured storage buckets, and authentication flows with gaps. The fundamentals cover the vast majority of real-world risk.

Authentication Done Right

Don't build your own. Use a maintained identity provider or battle-tested library, enforce MFA for anything sensitive, and treat session management — expiry, rotation, revocation — as part of the feature, not an afterthought.

The Dependency Problem

Your application is mostly other people's code. Automate vulnerability scanning in CI, keep a lockfile, and have a process for emergency patches. The Log4j weekend taught everyone what not having one costs.

Validate at the Boundary

  • Parse, don't validate — convert untrusted input into typed structures early
  • Parameterize every database query, no exceptions
  • Encode output for its context: HTML, URL, SQL, shell
  • Set a strict Content-Security-Policy and let it do its job

"Security is not a product you buy or a sprint you finish. It's a property of how your team works."

Practice the Bad Day

Have an incident response plan and rehearse it. Know who rotates credentials, who talks to customers, and where the logs are — before 3 a.m. on the day you need them.