Should port 1433 ever be open to the internet?

No. Port 1433 should strictly remain inside an isolated private VPC or accessible only through an encrypted VPN to protect against brute-force exploits.

How do I change the default MS SQL port?

Open SQL Server Configuration Manager, navigate to SQL Server Network Configuration -> Protocols -> TCP/IP Properties, and change the TCP Port setting under IPAll.

How can I test if port 1433 is reachable?

Use our Open Port Checker tool to confirm whether your server is accidentally exposing port 1433 to the outside world.

Home/Open Port Checker/Port 1433

Port 1194 Port 3306

Registered Port Reference

Port 1433: Microsoft SQL Server (TCP)

Relational database listener for Microsoft SQL Server enterprise database instances.

Port Number

1433

Transport

TCP

Security Risk

Critical

Standard / RFC

MS-TDS

Test Port 1433 Reachability Live

Verify whether Port 1433 is open, closed, or filtered on your server or public IP address.

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Service Architecture & Function

Port 1433 is the default TCP listening port for Microsoft SQL Server database engine instances. Client applications, web backends, and SQL Server Management Studio (SSMS) connect to port 1433 using the Tabular Data Stream (TDS) protocol.

Security Profile & Hardening

Exposing port 1433 directly to the public internet is a major security vulnerability. Attackers routinely scan for open SQL Server ports to execute password brute-forcing, remote code execution (xp_cmdshell), and ransomware deployment. Never expose port 1433 publicly; restrict it to private subnets or VPNs.

Example Firewall Commands:

# UFW (Ubuntu/Debian)

sudo ufw allow from 10.0.0.0/8 to any port 1433 proto tcp

# iptables (Direct Kernel)

iptables -A INPUT -p tcp -s 10.0.0.0/8 --dport 1433 -j ACCEPT