Open Ports Explained: Which Ones Are Actually Dangerous?

Every server has thousands of numbered 'ports' — think of them as different doors into the same building, each used for a different kind of traffic. An 'open' port means something on the server is listening for connections on that door. Not every open port is dangerous, but some are far riskier than others to leave exposed to the public internet.

Ports That Are Usually Fine to Expose

Port 80 (HTTP) and 443 (HTTPS) are meant to be public — that's how visitors reach your website. Leaving these open is completely normal and expected.

Ports That Are Risky to Expose Publicly

Database ports like 3306 (MySQL), 5432 (PostgreSQL), 6379 (Redis), and 27017 (MongoDB) are designed for internal use by your application — not the public internet. If exposed without authentication, attackers can attempt to connect directly and read or destroy your data. Similarly, 3389 (RDP) and 22 (SSH) provide remote access to the server itself; leaving these open to the world invites brute-force login attempts around the clock.

What To Do Instead

In most setups, database and remote-access ports should only be reachable from specific trusted IP addresses (like your office or VPN), never the open internet. Cloud firewalls and security groups are the standard way to restrict this, and most hosting providers make it straightforward to configure.

Check What's Exposed on Your Server

Nexora Shield's Port Scanner checks over 20 commonly exposed ports on any domain or IP, flagging which ones are open so you can review whether they should be.