Description

Network security groups should be periodically evaluated for port misconfigurations. Where certain ports and protocols may be exposed to the Internet, they should be evaluated for necessity and restricted wherever they are not explicitly required.

Rationale

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 Portal

Open the Networking blade for the specific Virtual machine in Azure portal.
Verify that the INBOUND PORT RULES does not have a rule for SSH such as.
- port = 22.
- protocol = TCP OR ANY.
- Source = Any OR Internet.

From Azure CLI

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" or "*" 
"sourceAddressPrefix" : "*" or "0.0.0.0" or "<nw>/0" or "/0" or "internet" or "any"

From Azure Policy

If referencing a digital copy of this Benchmark, clicking a Policy ID will open a link to the associated Policy definition in Azure.

Policy ID: 22730e10-96f6-4aac-ad84-9383d35b5917 - Name: Management ports should be closed on your virtual machines

Default Value

By default, SSH access from internet is not enabled.

Rationale​

Audit​

From Azure Portal​

From Azure CLI​

From Azure Policy​

Default Value​

References​