Description:

CloudWatch is a monitoring and management service that provides data and actionable insights for AWS, hybrid, and on-premises applications and infrastructure resources. Using this service you can collect and access all your performance and operational data in form of logs and metrics from a single platform.

When performing any activities on Application and infrastructure resources it generates lots of operational and monitoring data in form of logs and metrics. On Amazon, CloudWatch correlates metrics and logs through the visualized data sets in a single platform. So, We can quickly diagnose the problem to understand the root cause.


Rational:

Real-time monitoring of route table changes can be achieved by directing CloudTrail Logs to CloudWatch Logs and establishing corresponding metric filters and alarms. It is recommended that a metric filter and alarm be established for route table changes.


Impact:

The preceding rules together provide clear insight into route table changes and will notify you if it breaks the rule.


Default value:

By default, Metric Filter and CloudWatch alarm for route table changes will not exist.


Pre-Requisite:

  1. Sign in as admin or IAM user with required permissions

  2. Need SNS topic with a subscription for notification


Remediation:

Test Plan:

  1. Log in to the AWS Management Console and go to Cloudwatch dashboard at https://console.aws.amazon.com/cloudwatch/
  2. In the left navigation panel click on Log groups and select the log group you want to examine
  3. Go to the metric filter tab and Search for the metric filter related to route table changes 

If no metric filter showed up it means route table changes are not monitored by the cloud watch


Using AWS CLI:

To describe the Cloudwatch metrics

aws cloudwatch describe-metric-filters --log-group-name <value>


Implementation Steps:

  1. Log in to the AWS Management Console and go to Cloudwatch dashboard at https://console.aws.amazon.com/cloudwatch/

  2. In the left navigation, pane click on Log groups under Logs

  3. Select the log group for which you want to create a metric filter 

  4. Click on the Actions drop-down menu, select create a metric filter

  5. In the Create metric filter page, we define the filter pattern as { ($.eventName = CreateRoute) || ($.eventName = CreateRouteTable) || ($.eventName = ReplaceRoute) || ($.eventName = ReplaceRouteTableAssociation) || ($.eventName = DeleteRouteTable) || ($.eventName = DeleteRoute) || ($.eventName = DisassociateRouteTable) }and then click on Next button

  6. On Assign metric page, under the Create filter name give the filter name as RouteTable_changes

  7. Under the Metric Details section, provide the details required like Metric namespace, Metric name, metric value, and Default value(optional), and then click on the Next button 

  8. Review the details provided and click on Create metric filter button to create it

  9. After clicking on create metric filter You will see a metric filters page, Select the metric filter you have created and click on create an alarm on the right side of the Metric filters section.

  10. After clicking on create alarm you will be redirected to the next tab to Create Alarm, define the following:-

    • Metric name (it automatically takes from the metric filter)

    • Statistic select Sum

    • Period as 5minutes

  11. In the conditions section select the Threshold type to Static, Define the alarm condition with a Greater(>) threshold and give the value of threshold as you defined in metric value then click on the Next button

  12. Next is Configure actions in this choose Alarm state trigger option as In alarm, For SNS topic select SNS if exist or can create a new topic, click on NEXT

  13. Give the Name of Alarm e.g. ApiCallMonitoring and Alarm description(optional), click on the Next button.

  14. Review all the entered details and click on create Alarm


Using AWS CLI:

To create metric filter

put-metric-filter
--log-group-name <value>
--filter-name <value>
--filter-pattern <value>
--metric-transformations <value>

To create Alarm

aws cloudwatch put-metric-alarm 
--alarm-name <value>
--metric-name <value> 
--statistic Sum --period 300 --threshold <value>
--comparison-operator <value>
--evaluation-periods 1 -namespace '<give the name space>' 
--alarm-actions <sns_topic_arn>


Backout plan: 

  1. Log in to the AWS Management Console and go to Cloudwatch dashboard at https://console.aws.amazon.com/cloudwatch/

  2. In the left navigation, pane click on Log groups under Logs

  3. Select the log group you want to modify, go-to metric filter tab

  4. Choose the metric filter you want to delete and click on Delete

  5. Click on In Alarms in the left navigation pane

  6. Select the alarm you want to delete, click on the Actions drop-down, and select Delete

Using AWS CLI:

The following command deletes a log group named :  

aws logs delete-log-group --log-group-name <name_the group logs>

The delete-alarms command to delete the Amazon CloudWatch alarm   

aws cloudwatch delete-alarms --alarm-names <value>


Reference:

Amazon CloudWatch concepts - Amazon CloudWatch