ELB application load balancers should be configured with defensive or strictest desync mitigation mode¶

This control checks whether an Application Load Balancer is configured with defensive or strictest desync mitigation mode. The control fails if an Application Load Balancer is not configured with defensive or strictest desync mitigation mode.

How to fix¶

Attribute desync_mitigation_mode of aws_lb must be one of: "defensive", "strictest".

Implementation options¶

Choose the option that matches how you manage Terraform. All options satisfy this control.

Option 1: Compliance.tf module (recommended)¶

Use the compliance.tf registry module to get this control enforced by default. This control is mapped to the frameworks shown in the tabs above. To begin, see get started with compliance.tf.

module "alb" {
  source  = "nistcsfv11.compliance.tf/terraform-aws-modules/alb/aws"
  version = ">=10.0.0,<11.0.0"

  access_logs = {
    bucket = "example-bucket-abc123"
  }
  load_balancer_type = "application"
  name               = "abc123"
  security_groups    = ["sg-abc12345"]
  subnets            = ["subnet-abc123", "subnet-def456"]
  target_groups = {
    default = {
      create_attachment = false
      name_prefix       = "def-"
      port              = 443
      protocol          = "HTTPS"
      target_type       = "ip"
    }
  }
  vpc_id = "vpc-12345678"

  desync_mitigation_mode = "defensive"
}

module "alb" {
  source  = "pcidssv321.compliance.tf/terraform-aws-modules/alb/aws"
  version = ">=10.0.0,<11.0.0"

  access_logs = {
    bucket = "example-bucket-abc123"
  }
  load_balancer_type = "application"
  name               = "abc123"
  security_groups    = ["sg-abc12345"]
  subnets            = ["subnet-abc123", "subnet-def456"]
  target_groups = {
    default = {
      create_attachment = false
      name_prefix       = "def-"
      port              = 443
      protocol          = "HTTPS"
      target_type       = "ip"
    }
  }
  vpc_id = "vpc-12345678"

  desync_mitigation_mode = "defensive"
}

Option 2: Open source module (terraform-aws-modules)¶

If you use terraform-aws-modules/alb/aws, configure the required module inputs to satisfy this control. You can later migrate to the compliance.tf module with minimal changes because it is compatible by design.

module "alb" {
  source  = "terraform-aws-modules/alb/aws"
  version = ">=10.0.0,<11.0.0"

  access_logs = {
    bucket = "example-bucket-abc123"
  }
  load_balancer_type = "application"
  name               = "abc123"
  security_groups    = ["sg-abc12345"]
  subnets            = ["subnet-abc123", "subnet-def456"]
  target_groups = {
    default = {
      create_attachment = false
      name_prefix       = "def-"
      port              = 443
      protocol          = "HTTPS"
      target_type       = "ip"
    }
  }
  vpc_id = "vpc-12345678"

  desync_mitigation_mode = "defensive"
}

Option 3: Terraform AWS provider resources¶

If you manage resources directly, configure the relevant Terraform AWS provider resources to meet this control. See docs for the resources involved: aws_lb.

resource "aws_lb" "this" {
  access_logs {
    bucket = "pofix-example-lb-logs"
  }
  internal = true
  name     = "pofix-example-lb"
  subnets  = ["subnet-abc123", "subnet-def456"]

  desync_mitigation_mode = "defensive"
}

Tool mappings¶

Use these identifiers to cross-reference this control across tools, reports, and evidence.

• Compliance.tf (CTF) Control: elb_application_lb_desync_mitigation_mode

• AWS Config Managed Rule: ALB_DESYNC_MODE_CHECK

• Checkov Check: CKV_AWS_328

• Powerpipe Control: aws_compliance.control.elb_application_lb_desync_mitigation_mode