lacework-global-569

6.2 Evaluate and restrict SSH access from the Internet (Automated)

Profile Applicability

• Level 1

Description

Network security groups should be periodically evaluated for port misconfigurations. If a network security group exposes certain ports and protocols to the Internet, evaluate them for necessity and restrict 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

1. Open the Networking blade for the specific Virtual machine in Azure portal
2. Verify that the INBOUND PORT RULES does not have a rule for SSH such as
   • port = 22,
   • protocol = TCP,
   • 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"
"sourceAddressPrefix" : "*" or "0.0.0.0" or "<nw>/0" or "/0" or "internet" or "any"

Remediation

Where SSH is not explicitly required and narrowly configured for resources attached to the Network Security Group, restrict or eliminate Internet-level access to your Azure resources.

For internal access to relevant resources, configure an encrypted network tunnel such as:

ExpressRoute

Site-to-site VPN

Point-to-site VPN

References

https://docs.microsoft.com/en-us/azure/security/azure-security-network-security-best-practices#disable-rdpssh-access-to-azure-virtual-machines
https://docs.microsoft.com/en-us/security/benchmark/azure/security-controls-v3-network-security#ns-1-establish-network-segmentation-boundaries
Express Route
https://docs.microsoft.com/en-us/azure/expressroute/
Site-to-Site VPN
https://docs.microsoft.com/en-us/azure/vpn-gateway/vpn-gateway-howto-site-to-site-resource-manager-portal
Point-to-Site VPN
https://docs.microsoft.com/en-us/azure/vpn-gateway/vpn-gateway-howto-point-to-site-resource-manager-portal