Sensitive port is exposed to entire network
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Id: 594c198b-4d79-41b8-9b36-fde13348b619
Cloud Provider: Azure
Platform: Terraform
Severity: High
Category: Networking and Firewall
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Description
This check identifies Azure network security rules that expose sensitive ports (such as 23 [Telnet], 110 [POP3], or others) to the entire internet, creating a significant security vulnerability. When sensitive ports are accessible from any source IP (/0, 0.0.0.0/0, or similar notation), attackers can exploit these services to gain unauthorized access, perform reconnaissance, or execute service-specific attacks. To remediate this issue, either deny access to these ports, restrict access to specific IP addresses, or change the protocol. For example, use access = "Deny" for sensitive ports, or replace source_address_prefix = "0.0.0.0/0" or source_address_prefix = "/0" with a more restrictive value such as source_address_prefix = "192.168.0.0".
Compliant Code Examples
resource "azurerm_network_security_rule" "negative1" {
name = "example"
priority = 100
direction = "Inbound"
access = "Deny"
protocol = "TCP"
source_port_range = "*"
destination_port_range = "23"
source_address_prefix = "*"
destination_address_prefix = "*"
resource_group_name = azurerm_resource_group.example.name
network_security_group_name = azurerm_network_security_group.example.name
}
resource "azurerm_network_security_rule" "negative2" {
name = "example"
priority = 100
direction = "Inbound"
access = "Allow"
protocol = "Icmp"
source_port_range = "*"
destination_port_range = "23-34"
source_address_prefix = "*"
destination_address_prefix = "*"
resource_group_name = azurerm_resource_group.example.name
network_security_group_name = azurerm_network_security_group.example.name
}
resource "azurerm_network_security_rule" "negative3" {
name = "example"
priority = 100
direction = "Inbound"
access = "Allow"
protocol = "TCP"
source_port_range = "*"
destination_port_range = "8-174"
source_address_prefix = "0.0.0.0"
destination_address_prefix = "*"
resource_group_name = azurerm_resource_group.example.name
network_security_group_name = azurerm_network_security_group.example.name
}
resource "azurerm_network_security_rule" "negative4" {
name = "example"
priority = 100
direction = "Inbound"
access = "Allow"
protocol = "TCP"
source_port_range = "*"
destination_port_range = "23-196"
source_address_prefix = "192.168.0.0"
destination_address_prefix = "*"
resource_group_name = azurerm_resource_group.example.name
network_security_group_name = azurerm_network_security_group.example.name
}
resource "azurerm_network_security_rule" "negative5" {
name = "example"
priority = 100
direction = "Inbound"
access = "Allow"
protocol = "TCP"
source_port_range = "*"
destination_port_range = "23"
source_address_prefix = "/1"
destination_address_prefix = "*"
resource_group_name = azurerm_resource_group.example.name
network_security_group_name = azurerm_network_security_group.example.name
}
resource "azurerm_network_security_rule" "negative6" {
name = "example"
priority = 100
direction = "Inbound"
access = "Allow"
protocol = "*"
source_port_range = "*"
destination_port_range = "43"
source_address_prefix = "/0"
destination_address_prefix = "*"
resource_group_name = azurerm_resource_group.example.name
network_security_group_name = azurerm_network_security_group.example.name
}
resource "azurerm_network_security_rule" "negative7" {
name = "example"
priority = 100
direction = "Inbound"
access = "Allow"
protocol = "Icmp"
source_port_range = "*"
destination_port_range = "23"
source_address_prefix = "internet"
destination_address_prefix = "*"
resource_group_name = azurerm_resource_group.example.name
network_security_group_name = azurerm_network_security_group.example.name
}
resource "azurerm_network_security_rule" "negative8" {
name = "example"
priority = 100
direction = "Inbound"
access = "Allow"
protocol = "*"
source_port_range = "*"
destination_port_range = "22, 24,49-67"
source_address_prefix = "any"
destination_address_prefix = "*"
resource_group_name = azurerm_resource_group.example.name
network_security_group_name = azurerm_network_security_group.example.name
}
resource "azurerm_network_security_rule" "negative9" {
name = "example"
priority = 100
direction = "Inbound"
access = "Allow"
protocol = "Icmp"
source_port_range = "*"
destination_port_range = "23"
source_address_prefix = "/0"
destination_address_prefix = "*"
resource_group_name = azurerm_resource_group.example.name
network_security_group_name = azurerm_network_security_group.example.name
}
resource "azurerm_network_security_rule" "negative10" {
name = "example"
priority = 100
direction = "Inbound"
access = "Allow"
protocol = "TCP"
source_port_range = "*"
destination_port_range = "23 , 69"
source_address_prefix = "0.0.1.0"
destination_address_prefix = "*"
resource_group_name = azurerm_resource_group.example.name
network_security_group_name = azurerm_network_security_group.example.name
}
resource "azurerm_network_security_rule" "negative11" {
name = "example"
priority = 100
direction = "Inbound"
access = "Allow"
protocol = "TCP"
source_port_range = "*"
destination_port_range = "2,310"
source_address_prefix = "0.0.0.0"
destination_address_prefix = "*"
resource_group_name = azurerm_resource_group.example.name
network_security_group_name = azurerm_network_security_group.example.name
}
Non-Compliant Code Examples
resource "azurerm_network_security_rule" "positive1" {
name = "example"
priority = 100
direction = "Inbound"
access = "Allow"
protocol = "UDP"
source_port_range = "*"
destination_port_range = "61621"
source_address_prefix = "/0"
destination_address_prefix = "*"
resource_group_name = azurerm_resource_group.example.name
network_security_group_name = azurerm_network_security_group.example.name
}
resource "azurerm_network_security_rule" "positive2" {
name = "example"
priority = 100
direction = "Inbound"
access = "Allow"
protocol = "TCP"
source_port_range = "*"
destination_port_range = "23-34"
source_address_prefix = "1.1.1.1/0"
destination_address_prefix = "*"
resource_group_name = azurerm_resource_group.example.name
network_security_group_name = azurerm_network_security_group.example.name
}
resource "azurerm_network_security_rule" "positive3" {
name = "example"
priority = 100
direction = "Inbound"
access = "Allow"
protocol = "*"
source_port_range = "*"
destination_port_range = "21-23"
source_address_prefix = "/0"
destination_address_prefix = "*"
resource_group_name = azurerm_resource_group.example.name
network_security_group_name = azurerm_network_security_group.example.name
}
resource "azurerm_network_security_rule" "positive4" {
name = "example"
priority = 100
direction = "Inbound"
access = "Allow"
protocol = "*"
source_port_range = "*"
destination_port_range = "23"
source_address_prefix = "0.0.0.0/0"
destination_address_prefix = "*"
resource_group_name = azurerm_resource_group.example.name
network_security_group_name = azurerm_network_security_group.example.name
}
resource "azurerm_network_security_rule" "positive5" {
name = "example"
priority = 100
direction = "Inbound"
access = "Allow"
protocol = "UDP"
source_port_range = "*"
destination_port_range = "23,245"
source_address_prefix = "34.15.11.3/0"
destination_address_prefix = "*"
resource_group_name = azurerm_resource_group.example.name
network_security_group_name = azurerm_network_security_group.example.name
}
resource "azurerm_network_security_rule" "positive6" {
name = "example"
priority = 100
direction = "Inbound"
access = "Allow"
protocol = "TCP"
source_port_range = "*"
destination_port_range = "23"
source_address_prefix = "/0"
destination_address_prefix = "*"
resource_group_name = azurerm_resource_group.example.name
network_security_group_name = azurerm_network_security_group.example.name
}
resource "azurerm_network_security_rule" "positive7" {
name = "example"
priority = 100
direction = "Inbound"
access = "Allow"
protocol = "UDP"
source_port_range = "*"
destination_port_range = "22-64, 94"
source_address_prefix = "10.0.0.0/0"
destination_address_prefix = "*"
resource_group_name = azurerm_resource_group.example.name
network_security_group_name = azurerm_network_security_group.example.name
}
resource "azurerm_network_security_rule" "positive8" {
name = "example"
priority = 100
direction = "Inbound"
access = "Allow"
protocol = "TCP"
source_port_range = "*"
destination_port_range = "14, 23, 48"
source_address_prefix = "12.12.12.12/0"
destination_address_prefix = "*"
resource_group_name = azurerm_resource_group.example.name
network_security_group_name = azurerm_network_security_group.example.name
}
resource "azurerm_network_security_rule" "positive9" {
name = "example"
priority = 100
direction = "Inbound"
access = "Allow"
protocol = "*"
source_port_range = "*"
destination_port_range = "12, 23-24,46"
source_address_prefix = "/0"
destination_address_prefix = "*"
resource_group_name = azurerm_resource_group.example.name
network_security_group_name = azurerm_network_security_group.example.name
}
resource "azurerm_network_security_rule" "positive10" {
name = "example"
priority = 100
direction = "Inbound"
access = "Allow"
protocol = "*"
source_port_range = "*"
destination_port_range = "46-146, 18-36, 1-2, 3"
source_address_prefix = "1.2.3.4/0"
destination_address_prefix = "*"
resource_group_name = azurerm_resource_group.example.name
network_security_group_name = azurerm_network_security_group.example.name
}
