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Network security groups should not permit ingress from the internet to UDP ports Affecting Network service in Azure

Severity

0.0
medium
0
10
    Severity Framework
    Snyk CCSS
    Rule category
    Network / Ports

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    Frameworks
    CIS-Azure
  • Snyk ID SNYK-CC-00694
  • credit Snyk Research Team
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Description

Broadly exposing UDP services over the internet enables malicious actors to use DDoS amplification techniques to reflect spoofed UDP traffic from virtual machines.

How to fix?

Set the securityRules.properties.access attribute of Microsoft.Network/networkSecurityGroups or properties.access attribute of Microsoft.Network/networkSecurityGroups/securityRules to Deny.

Example Configuration

{
    "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
    "contentVersion": "1.0.0.0",
    "parameters": {},
    "variables": {},
    "resources": [
       {
            "type": "Microsoft.Network/networkSecurityGroups",
            "apiVersion": "2022-07-01",
            "name": "example-sg694-allowed1",
            "location": "[resourceGroup().location]",
            "properties": {
                "securityRules": [
                    {
                        "name": "security-rule6941",
                        "properties": {
                            "priority": 100,
                            "direction": "Inbound",
                            "access": "Deny",
                            "protocol": "Udp",
                            "sourcePortRange": "*",
                            "destinationPortRange": "*",
                            "sourceAddressPrefixes": [
                                "0.0.0.0"
                            ],
                            "destinationAddressPrefix": "*"
                        }
                    },
                    {
                        "name": "security-rule6942",
                        "properties": {
                            "priority": 400,
                            "direction": "Inbound",
                            "access": "Deny",
                            "protocol": "Udp",
                            "sourcePortRange": "*",
                            "destinationPortRange": "*",
                            "sourceAddressPrefixes": [
                                "0.0.0.0"
                            ],
                            "destinationAddressPrefix": "*"
                        }
                    }
                ]
            }
        }
    ]
}