Control: 8.1 Ensure that RDP access from the Internet is evaluated and restricted

Description

Network security groups should be periodically evaluated for port misconfigurations. Where RDP is not explicitly required and narrowly configured for resources attached to a network security group, Internet-level access to Azure resources should be restricted or eliminated.

The potential security problem with using RDP 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 an Azure Virtual Network or even attack networked devices outside of Azure.

Remediation

From Azure Portal

Go to Network security groups.
Under Settings, click Inbound security rules.
Check the box next to any inbound security rule matching:

Port: 3389 or range including 3389
Protocol: TCP or Any
Source: 0.0.0.0/0, Internet, or Any
Action: Allow

Click Delete.
Click Yes.

From Azure CLI

For each network security group rule requiring remediation, run the following command to delete a rule:

az network nsg rule delete --resource-group <resource-group> --nsg-name <network-security-group> --name <rule>

Default Value

By default, RDP access from internet is not enabled.

Usage

Run the control in your terminal:

powerpipe control run azure_compliance.control.cis_v400_8_1

Snapshot and share results via Turbot Pipes:

powerpipe login
powerpipe control run azure_compliance.control.cis_v400_8_1 --share

SQL

This control uses a named query:

with network_sg as (
  select
    distinct name sg_name
  from
    azure_network_security_group nsg,
    jsonb_array_elements(security_rules) sg,
    jsonb_array_elements_text(sg -> 'properties' -> 'destinationPortRanges' || (sg -> 'properties' -> 'destinationPortRange') :: jsonb) dport,
    jsonb_array_elements_text(sg -> 'properties' -> 'sourceAddressPrefixes' || (sg -> 'properties' -> 'sourceAddressPrefix') :: jsonb) sip
  where
    sg -> 'properties' ->> 'access' = 'Allow'
    and sg -> 'properties' ->> 'direction' = 'Inbound'
    and (sg -> 'properties' ->> 'protocol' ilike 'TCP' or sg -> 'properties' ->> 'protocol' = '*')
    and sip in ('*', '0.0.0.0', '0.0.0.0/0', 'Internet', 'any', '<nw>/0', '/0')
    and (
      dport in ('3389', '*')
      or (
        dport like '%-%'
        and split_part(dport, '-', 1) :: integer <= 3389
        and split_part(dport, '-', 2) :: integer >= 3389
      )
    )
)
select
  sg.id resource,
  case
    when nsg.sg_name is null then 'ok'
    else 'alarm'
  end as status,
  case
    when nsg.sg_name is null
      then sg.title || ' restricts RDP access from internet.'
    else sg.title || ' allows RDP access from internet.'
  end as reason
  
  , sg.resource_group as resource_group
  , sub.display_name as subscription
from
  azure_network_security_group sg
  left join network_sg nsg on nsg.sg_name = sg.name
  join azure_subscription sub on sub.subscription_id = sg.subscription_id;