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# AWS Elastic Load Balancer (Classic) with cross-zone load balancing disabled misconfiguration detecte

## Rule Details

|                        |                                      |
| ---------------------- | ------------------------------------ |
| Cortex AppSec Rule ID  | APPSEC\_AWS\_138                     |
| Category - Subcategory | Public Exposure - Load Balancing     |
| Provider               | AWS                                  |
| Severity               | LOW                                  |
| Framework              | Terraform, Terraform Plan            |
| Mapped CSPM/KSPM Rule  | 194dc989-ec4c-426c-826f-d7365d9a59ed |

## Impact

Cross-zone load balancing reduces the need to maintain equivalent numbers of instances in each enabled Availability Zone, and improves your application's ability to handle the loss of one or more instances. This would also guarantee better fault tolerance and more consistent traffic flow. If one of the availability zones registered with the ELB fails (as result of network outage or power loss), the load balancer with the Cross-Zone Load Balancing activated would act as a traffic guard, stopping any request being sent to the unhealthy zone and routing it to the other zones.

## How to Fix

*Resource:* xyz

* *Arguments:* xyz \[this will be for composite checks and will indicate a specific resource] \[source,go]

***

resource "aws\_elb" "test\_success" { name = "foobar-terraform-elb" availability\_zones = \["us-west-2a", "us-west-2b", "us-west-2c"] access\_logs { bucket = "foo" bucket\_prefix = "bar" interval = 60 } listener { instance\_port = 8000 instance\_protocol = "http" lb\_port = 80 lb\_protocol = "http" } listener { instance\_port = 8000 instance\_protocol = "http" lb\_port = 443 lb\_protocol = "https" ssl\_certificate\_id = "arn:aws:iam::123456789012:server-certificate/certName" } health\_check { healthy\_threshold = 2 unhealthy\_threshold = 2 timeout = 3 target = "HTTP:8000/" interval = 30 } instances = \[aws\_instance.foo.id] idle\_timeout = 400 connection\_draining = true connection\_draining\_timeout = 400 } """) resource\_conf = hcl\_res\['resource']\[0]\['aws\_elb']\['test\_success'] scan\_result = check.scan\_resource\_conf(conf=resource\_conf) self.assertEqual(CheckResult.PASSED, scan\_result)

def test\_success(self): hcl\_res = hcl2.loads(""" resource "aws\_elb" "test\_success" { name = "foobar-terraform-elb" availability\_zones = \["us-west-2a", "us-west-2b", "us-west-2c"] access\_logs { bucket = "foo" bucket\_prefix = "bar" interval = 60 } listener { instance\_port = 8000 instance\_protocol = "http" lb\_port = 80 lb\_protocol = "http" } listener { instance\_port = 8000 instance\_protocol = "http" lb\_port = 443 lb\_protocol = "https" ssl\_certificate\_id = "arn:aws:iam::123456789012:server-certificate/certName" } health\_check { healthy\_threshold = 2 unhealthy\_threshold = 2 timeout = 3 target = "HTTP:8000/" interval = 30 } instances = \[aws\_instance.foo.id]

* cross\_zone\_load\_balancing = true idle\_timeout = 400 connection\_draining = true connection\_draining\_timeout = 400 }

***


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