Profile Applicability: Level 2


Description: 

Real-time monitoring of API calls can be achieved by directing CloudTrail Logs to CloudWatch Logs and establishing corresponding metric filters and alarms. Security Groups are a stateful packet filter that controls ingress and egress traffic within a VPC. It is recommended that a metric filter and alarm be established changes to Security Groups. 


Rationale: 

Monitoring changes to security group will help ensure that resources and services are not unintentionally exposed. 


Audit: 

Perform the following to ensure that there is at least one active multi-region CloudTrail with prescribed metric filters and alarms configured: 

1. Identify the log group name configured for use with active multi-region CloudTrail:  List all CloudTrails: aws cloudtrail describe-trails  Identify Multi region Cloudtrails: Trails with "IsMultiRegionTrail" set to true  From value associated with CloudWatchLogsLogGroupArn 

2. Get a list of all associated metric filters for this : aws logs describe-metric-filters --log-group-name "" 

3. Ensure the output from the above command contains the following: "filterPattern": "{ ($.eventName = ConsoleLogin) && ($.errorMessage = "Failed authentication") }" 

4. Note the  value associated with the filterPattern found in step 3. 

5. Get a list of CloudWatch alarms and filter on the captured in step 4. aws cloudwatch describe-alarms --query 'MetricAlarms[?MetricName== ``]' 

6. Note the AlarmActions value - this will provide the SNS topic ARN value. 

7. Ensure there is at least one active subscriber to the SNS topic aws sns list-subscriptions-by-topic --topic-arn at least one subscription should have "SubscriptionArn" with valid aws ARN. Example of valid "SubscriptionArn": "arn:aws:sns::::"


Remediation:

Perform the following to setup the metric filter, alarm, SNS topic, and subscription: 

1. Create a metric filter based on filter pattern provided which checks for AWS Configuration changes and the  taken from audit step 1. aws logs put-metric-filter --log-group-name  -- filter-name `` --metric-transformations metricName= `` ,metricNamespace='CISBenchmark',metricValue=1 --filter-pattern '{ ($.eventName = ConsoleLogin) && ($.errorMessage = "Failed authentication") }' 

Note: You can choose your own metricName and metricNamespace strings. Using the same metricNamespace for all Foundations Benchmark metrics will group them together. 

2. Create an SNS topic that the alarm will notify aws sns create-topic --name Note: you can execute this command once and then re-use the same topic for all monitoring alarms. 

3. Create an SNS subscription to the topic created in step 2 aws sns subscribe --topic-arn  --protocol  - -notification-endpoint Note: you can execute this command once and then re-use the SNS subscription for all monitoring alarms. 

4. Create an alarm that is associated with the CloudWatch Logs Metric Filter created in step 1 and an SNS topic created in step 2 aws cloudwatch put-metric-alarm --alarm-name `` --metric-name `` --statistic Sum --period 300 --threshold 1 --comparison-operator GreaterThanOrEqualToThreshold --evaluation-periods 1 -- namespace 'CISBenchmark' --alarm-actions


Reference: 

1. CCE-79195-4 

2. https://docs.aws.amazon.com/awscloudtrail/latest/userguide/receive-cloudtraillog-files-from-multiple-regions.html 

3. https://docs.aws.amazon.com/awscloudtrail/latest/userguide/cloudwatch-alarmsfor-cloudtrail.html 

4. https://docs.aws.amazon.com/sns/latest/dg/SubscribeTopic.html

Notes: Configuring log metric filter and alarm on Multi-region (global) CloudTrail 

  • Ensures that activities from all regions (used as well as unused) are monitored 
  • Ensures that activities on all supported global services are monitored 
  • Ensures that all management events across all regions are monitored

CIS Controls:

4.8 Log and Alert on Changes to Administrative Group Membership 

Configure systems to issue a log entry and alert when an account is added to or removed from any group assigned administrative privileges.