Port 1433: Microsoft SQL Server
SQL Server database connections. Scanned and brute-forced constantly. Reach databases over a private network or VPN.
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Port 1433 at a glance
Port1433
ProtocolTCP
ServiceMicrosoft SQL Server
Open to the Internet?No, keep it on a private network
See What Is Listeningss -lntup | grep ':1433 '
Test From Outsidenc -zv your-server 1433
Block with UFWufw deny 1433/tcp
Block with nftablesnft add rule inet filter input tcp dport 1433 drop
Microsoft SQL Server uses TCP port 1433. SQL Server database connections.
Scanned and brute-forced constantly. Reach databases over a private network or VPN.
If ss shows something listening on port 1433 on a public address, bind it to 127.0.0.1 or a private interface in the service's own configuration, and drop the port in the firewall as well.
Other Ports
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Questions
What is port 1433 used for?
Microsoft SQL Server. SQL Server database connections.
Is it safe to open port 1433?
No, keep it on a private network. Scanned and brute-forced constantly. Reach databases over a private network or VPN.
How do I check if port 1433 is open?
On the server, ss -lntup | grep ':1433 ' shows what is listening. From another machine, nc -zv your-server 1433 shows whether the firewall lets it through.
How do I block port 1433?
With UFW: ufw deny 1433/tcp. With nftables, add a drop rule for dport 1433 in your input chain.
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