Azure Network Security Group having Inbound rule overly permissive to all traffic on UDP protocol

Description

Disable Internet exposed UDP ports on network security groups. The potential security problem with broadly exposing UDP services over the Internet is that attackers can use DDoS amplification techniques to reflect spoofed UDP traffic from Azure Virtual Machines. The most common types of these attacks use exposed DNS, NTP, SSDP, SNMP, CLDAP and other UDP-based services as amplification source for disrupting services of other machines on the Azure Virtual Network or even attack networked devices outside of Azure.

Code Example

resource "azurerm_network_security_group" "example" {

              security_rule {
                name                       = "test123"
                priority                   = 100
                direction                  = "Inbound"
+               access                     = "Deny"
+               protocol                   = "Udp"
                source_port_range          = "*"
                destination_port_range     = "*"
                source_address_prefix      = "*"
                destination_address_prefix = "*"
              }
                                ...
            }

Remediation

Terraform

• Resource: azurerm_network_security_group
• Arguments: protocol

Rule Details

Field	Value
ID	IAC-0585
Severity	MEDIUM
IaC Type	Terraform
Frameworks	Terraform,
Checkov ID	CKV_AZURE_77

References

• Checkov Rule

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