Port 1433 (TCP) — Microsoft SQL Server

MS SQL Server database.

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Databases should never be reachable from the internet.

Check if port 1433 is open

On the server, see what is listening:

sudo ss -tulpn | grep ':1433 '

From another machine, test reachability:

nc -zv your-server.example.com 1433

With UFW (Ubuntu/Debian):

sudo ufw deny 1433

With firewalld (RHEL/AlmaLinux/Rocky):

sudo firewall-cmd --permanent --remove-port=1433/tcp && sudo firewall-cmd --reload