Azure Networking - Ensure that SSH Access is Restricted from the Internet

Overview:

Disable SSH access on network security groups from the Internet.

Why:

The potential security problem with using SSH over the Internet is that attackers can use various brute force techniques to gain access to Azure Virtual Machines. Once the attackers gain access, they can use a virtual machine as a launch point for compromising other machines on the Azure Virtual Network or even attack networked devices outside of Azure.

Audit:

From Azure Command Line

List Network security groups with corresponding non-default Security rules:

az network nsg list --query [*].[name,securityRules] 

Ensure that none of the NSGs have security rule as below:

"access" : "Allow"
"destinationPortRange" : "22" or "*" or "[port range containing 22]" "direction" : "Inbound"
"protocol" : "TCP"
"sourceAddressPrefix" : "*" or "0.0.0.0" or "<nw>/0" or "/0" or "internet" or "any"

Fix

Disable direct SSH access to your Azure Virtual Machines from the Internet. After direct SSH access from the Internet is disabled, you have other options you can use to access these virtual machines for remote management:

Reference:

• https://docs.microsoft.com/en-us/azure/security/azure-security-network-security-best-practices%23disable-rdpssh-access-to-azure-virtual-machines