Issue with Unrestricted Telnet Access to Azure SQL Database Server Despite Firewall Rules

Mithila Lishan 71 Reputation points
2024-09-20T02:36:53.1133333+00:00

I have provisioned an Azure SQL Database server and configured the server security settings as follows:

  • Public access: Selected "Selected Networks"
  • Firewall rule: Whitelisted public IP addresses to allow access to the database

However, when I attempt to "telnet" to the server from a PC with a public IP that is not whitelisted, the connection still goes through.

What can I do to prevent telnet access while maintaining the same configurations?

Azure SQL Database
SQL Server
SQL Server
A family of Microsoft relational database management and analysis systems for e-commerce, line-of-business, and data warehousing solutions.
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Accepted answer
  1. Alberto Morillo 34,056 Reputation points MVP
    2024-09-20T02:49:50.2766667+00:00

    What is allowing telnet to connect is the Azure SQL Public Gateway not the Azure SQL Database itself. This is an expected behavior in Azure Database. Port 1433 is required to provide a variety of Azure services, and this is by design.

    So, telnet is reaching a public gateway that is open for everyone and is not reaching the actual database, Read here about the gateway

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