Open Telnet
Determines if TCP port 23 for Telnet is open to the public
While some ports such as HTTP and HTTPS are required to be open to the public to function properly, more sensitive services such as Telnet should be restricted to known IP addresses.
Recommended Actions
Follow the appropriate remediation steps below to resolve the issue.
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Log into the Google Cloud Platform Console.
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Scroll down the left navigation panel and choose the “Networking” to select the “Firewall rules” option under the “VPC network.”
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On the “Firewall rules” page, select the “Firewall rule” which needs to be verified.
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On the selected “Firewall rules”, if TCP port 23 for “Telnet” is open to the public then the selected “Firewall rule” is not as per the best standards.
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Repeat steps number 2 - 4 to verify another “Firewall rule” in the network.
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Navigate to “VPC network” and choose the “Firewall rules” option under the “Networking” and select the “Firewall rule” which needs to be restricted to known IP addresses.
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On the “Firewall rules” page, click on the “Edit” button at the top and under the “Source IP ranges” enter the IP addresses as per the requirements.
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Click on the “Save” button at the bottom to make the changes.
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Repeat steps number 6 - 8 to restrict TCP port 23 to known IP addresses.