Implementing AWS Config Rules for Compliance

When to Use

• When establishing continuous compliance monitoring for AWS resources against regulatory standards
• When implementing automated detection and remediation of configuration drift
• When building a compliance dashboard across multiple AWS accounts using AWS Organizations
• When audit teams require evidence of continuous compliance rather than point-in-time assessments
• When deploying guardrails that detect non-compliant resources within minutes of creation

Do not use for real-time threat detection (use GuardDuty), for application vulnerability scanning (use Inspector), or for one-time compliance assessments (use Prowler for faster ad-hoc audits).

Prerequisites

• AWS Config recording enabled in all target accounts and regions
• IAM role with config:*, ssm:*, and lambda:* permissions for rule management
• AWS Organizations with delegated administrator for Config aggregation
• S3 bucket for Config delivery channel and SNS topic for notifications
• CloudFormation StackSets or Terraform for multi-account rule deployment

Workflow

Step 1: Enable AWS Config Recording

Set up the Config recorder and delivery channel in each target account.

# Create S3 bucket for Config data
aws s3api create-bucket \
  --bucket config-compliance-data-ACCOUNT_ID \
  --region us-east-1

# Create Config service role
aws iam create-service-linked-role --aws-service-name config.amazonaws.com

# Start the Config recorder
aws configservice put-configuration-recorder \
  --configuration-recorder name=default,roleARN=arn:aws:iam::ACCOUNT:role/aws-service-role/config.amazonaws.com/AWSServiceRoleForConfig \
  --recording-group allSupported=true,includeGlobalResourceTypes=true

# Set up delivery channel
aws configservice put-delivery-channel \
  --delivery-channel '{
    "name": "default",
    "s3BucketName": "config-compliance-data-ACCOUNT_ID",
    "snsTopicARN": "arn:aws:sns:us-east-1:ACCOUNT:config-notifications",
    "configSnapshotDeliveryProperties": {"deliveryFrequency": "TwentyFour_Hours"}
  }'

# Start recording
aws configservice start-configuration-recorder --configuration-recorder-name default

Step 2: Deploy Managed Config Rules for CIS Compliance

Enable AWS-managed Config rules that map to CIS AWS Foundations Benchmark controls.

# S3 bucket security rules
aws configservice put-config-rule --config-rule '{
  "ConfigRuleName": "s3-bucket-public-read-prohibited",
  "Source": {"Owner": "AWS", "SourceIdentifier": "S3_BUCKET_PUBLIC_READ_PROHIBITED"}
}'

aws configservice put-config-rule --config-rule '{
  "ConfigRuleName": "s3-bucket-server-side-encryption-enabled",
  "Source": {"Owner": "AWS", "SourceIdentifier": "S3_BUCKET_SERVER_SIDE_ENCRYPTION_ENABLED"}
}'

aws configservice put-config-rule --config-rule '{
  "ConfigRuleName": "s3-bucket-ssl-requests-only",
  "Source": {"Owner": "AWS", "SourceIdentifier": "S3_BUCKET_SSL_REQUESTS_ONLY"}
}'

# IAM security rules
aws configservice put-config-rule --config-rule '{
  "ConfigRuleName": "iam-root-access-key-check",
  "Source": {"Owner": "AWS", "SourceIdentifier": "IAM_ROOT_ACCESS_KEY_CHECK"}
}'

aws configservice put-config-rule --config-rule '{
  "ConfigRuleName": "mfa-enabled-for-iam-console-access",
  "Source": {"Owner": "AWS", "SourceIdentifier": "MFA_ENABLED_FOR_IAM_CONSOLE_ACCESS"}
}'

aws configservice put-config-rule --config-rule '{
  "ConfigRuleName": "iam-password-policy",
  "Source": {"Owner": "AWS", "SourceIdentifier": "IAM_PASSWORD_POLICY"},
  "InputParameters": "{\"RequireUppercaseCharacters\":\"true\",\"RequireLowercaseCharacters\":\"true\",\"RequireSymbols\":\"true\",\"RequireNumbers\":\"true\",\"MinimumPasswordLength\":\"14\"}"
}'

# Network security rules
aws configservice put-config-rule --config-rule '{
  "ConfigRuleName": "restricted-ssh",
  "Source": {"Owner": "AWS", "SourceIdentifier": "INCOMING_SSH_DISABLED"}
}'

aws configservice put-config-rule --config-rule '{
  "ConfigRuleName": "vpc-flow-logs-enabled",
  "Source": {"Owner": "AWS", "SourceIdentifier": "VPC_FLOW_LOGS_ENABLED"}
}'

# Encryption rules
aws configservice put-config-rule --config-rule '{
  "ConfigRuleName": "rds-storage-encrypted",
  "Source": {"Owner": "AWS", "SourceIdentifier": "RDS_STORAGE_ENCRYPTED"}
}'

aws configservice put-config-rule --config-rule '{
  "ConfigRuleName": "encrypted-volumes",
  "Source": {"Owner": "AWS", "SourceIdentifier": "ENCRYPTED_VOLUMES"}
}'

Step 3: Create Custom Config Rules with Lambda

Build custom rules for organization-specific compliance requirements.

# custom_config_rule.py - Ensure EC2 instances have required tags
import json
import boto3

config = boto3.client('config')

REQUIRED_TAGS = ['Environment', 'Owner', 'CostCenter', 'Project']

def lambda_handler(event, context):
    invoking_event = json.loads(event['invokingEvent'])
    configuration_item = invoking_event.get('configurationItem', {})

    if configuration_item['resourceType'] != 'AWS::EC2::Instance':
        return

    tags = {t['key']: t['value'] for t in configuration_item.get('tags', [])}
    missing_tags = [tag for tag in REQUIRED_TAGS if tag not in tags]

    if missing_tags:
        compliance = 'NON_COMPLIANT'
        annotation = f"Missing required tags: {', '.join(missing_tags)}"
    else:
        compliance = 'COMPLIANT'
        annotation = 'All required tags present'

    config.put_evaluations(
        Evaluations=[{
            'ComplianceResourceType': configuration_item['resourceType'],
            'ComplianceResourceId': configuration_item['resourceId'],
            'ComplianceType': compliance,
            'Annotation': annotation,
            'OrderingTimestamp': configuration_item['configurationItemCaptureTime']
        }],
        ResultToken=event['resultToken']
    )

# Deploy the custom rule
aws configservice put-config-rule --config-rule '{
  "ConfigRuleName": "ec2-required-tags",
  "Source": {
    "Owner": "CUSTOM_LAMBDA",
    "SourceIdentifier": "arn:aws:lambda:us-east-1:ACCOUNT:function:config-required-tags",
    "SourceDetails": [{
      "EventSource": "aws.config",
      "MessageType": "ConfigurationItemChangeNotification"
    }]
  },
  "Scope": {"ComplianceResourceTypes": ["AWS::EC2::Instance"]}
}'

Step 4: Configure Automatic Remediation

Set up SSM Automation documents for automatic remediation of non-compliant resources.

# Auto-remediate public S3 buckets
aws configservice put-remediation-configurations --remediation-configurations '[{
  "ConfigRuleName": "s3-bucket-public-read-prohibited",
  "TargetType": "SSM_DOCUMENT",
  "TargetId": "AWS-DisableS3BucketPublicReadWrite",
  "Parameters": {
    "S3BucketName": {"ResourceValue": {"Value": "RESOURCE_ID"}},
    "AutomationAssumeRole": {"StaticValue": {"Values": ["arn:aws:iam::ACCOUNT:role/ConfigRemediationRole"]}}
  },
  "Automatic": true,
  "MaximumAutomaticAttempts": 3,
  "RetryAttemptSeconds": 60
}]'

# Auto-remediate unencrypted EBS volumes
aws configservice put-remediation-configurations --remediation-configurations '[{
  "ConfigRuleName": "encrypted-volumes",
  "TargetType": "SSM_DOCUMENT",
  "TargetId": "AWS-EnableEBSEncryptionByDefault",
  "Parameters": {
    "AutomationAssumeRole": {"StaticValue": {"Values": ["arn:aws:iam::ACCOUNT:role/ConfigRemediationRole"]}}
  },
  "Automatic": true,
  "MaximumAutomaticAttempts": 1,
  "RetryAttemptSeconds": 300
}]'

# Auto-remediate security groups allowing SSH from 0.0.0.0/0
aws configservice put-remediation-configurations --remediation-configurations '[{
  "ConfigRuleName": "restricted-ssh",
  "TargetType": "SSM_DOCUMENT",
  "TargetId": "AWS-DisablePublicAccessForSecurityGroup",
  "Parameters": {
    "GroupId": {"ResourceValue": {"Value": "RESOURCE_ID"}},
    "AutomationAssumeRole": {"StaticValue": {"Values": ["arn:aws:iam::ACCOUNT:role/ConfigRemediationRole"]}}
  },
  "Automatic": true,
  "MaximumAutomaticAttempts": 3,
  "RetryAttemptSeconds": 60
}]'

Step 5: Set Up Multi-Account Aggregation

Aggregate compliance data from all organization accounts into a central view.

# Create a Config aggregator for the organization
aws configservice put-configuration-aggregator \
  --configuration-aggregator-name org-compliance-aggregator \
  --organization-aggregation-source '{
    "RoleArn": "arn:aws:iam::ACCOUNT:role/ConfigAggregatorRole",
    "AllAwsRegions": true
  }'

# Query aggregate compliance across all accounts
aws configservice get-aggregate-compliance-details-by-config-rule \
  --configuration-aggregator-name org-compliance-aggregator \
  --config-rule-name s3-bucket-public-read-prohibited \
  --compliance-type NON_COMPLIANT \
  --query 'AggregateEvaluationResults[*].[AccountId,AwsRegion,EvaluationResultIdentifier.EvaluationResultQualifier.ResourceId,ComplianceType]' \
  --output table

# Get compliance summary by account
aws configservice get-aggregate-compliance-summary-by-source \
  --configuration-aggregator-name org-compliance-aggregator \
  --query 'AggregateComplianceCounts[*].[GroupName,ComplianceSummary.CompliantResourceCount.CappedCount,ComplianceSummary.NonCompliantResourceCount.CappedCount]' \
  --output table

Key Concepts

Tools & Systems

• AWS Config: Continuous configuration recording and compliance evaluation service for AWS resources
• SSM Automation: AWS Systems Manager documents for executing automated remediation actions on non-compliant resources
• Config Conformance Packs: Pre-built rule collections for CIS, PCI DSS, NIST 800-53, and HIPAA compliance
• CloudFormation StackSets: Multi-account deployment mechanism for Config rules across AWS Organizations
• Config Aggregator: Cross-account and cross-region compliance data consolidation

Common Scenarios

Scenario: Deploying CIS Compliance Monitoring Across 30 AWS Accounts

Context: A financial services company needs to demonstrate continuous CIS AWS Foundations Benchmark compliance across all 30 production accounts for their annual SOC 2 audit.

Approach:

1. Enable AWS Config recording in all accounts via CloudFormation StackSets
2. Deploy the CIS conformance pack to all accounts using StackSets
3. Set up a Config aggregator in the security account for organization-wide visibility
4. Configure auto-remediation for safe-to-fix rules (public S3, unencrypted volumes)
5. Create EventBridge rules to alert on new NON_COMPLIANT evaluations
6. Build a weekly compliance report aggregating scores across all accounts
7. Store Config snapshots in S3 with lifecycle policies for audit retention

Pitfalls: Config recording incurs costs per configuration item recorded. In accounts with many resources, costs can be significant. Use targeted recording groups to focus on compliance-relevant resource types rather than recording all resources. Auto-remediation of network rules (security groups) can disrupt applications if the rule was intentionally permissive.

Output Format

AWS Config Compliance Report
===============================
Organization: Acme Financial (30 accounts)
Framework: CIS AWS Foundations 1.4
Report Date: 2026-02-23
Config Rules Active: 48

COMPLIANCE SUMMARY:
  Overall Compliance: 87%
  Compliant Resources:     4,234
  Non-Compliant Resources:   612
  Not Applicable:            189

TOP NON-COMPLIANT RULES:
  encrypted-volumes:              89 resources (14 accounts)
  vpc-flow-logs-enabled:          67 resources (12 accounts)
  mfa-enabled-for-iam-console:    45 resources (8 accounts)
  s3-bucket-ssl-requests-only:    34 resources (6 accounts)
  restricted-ssh:                 28 resources (5 accounts)

AUTO-REMEDIATION (Last 30 Days):
  Public S3 buckets remediated:    12
  Security groups restricted:       8
  EBS default encryption enabled:   6
  Total auto-remediated:           26
  Failed remediation attempts:      3

ACCOUNT COMPLIANCE RANKING:
  1. prod-core (account-001):     96% compliant
  2. prod-data (account-002):     94% compliant
  ...
  30. dev-sandbox (account-030):  68% compliant