Alarm for denied connections in CloudFront logs should be configured

Description

Alarms should be configured to alert users to denied connections to CloudFront distributions so users can investigate anomalous traffic.

Console Remediation Steps

  • Navigate to CloudFront.

  • Under Reports & analytics, select Alarms.

  • Click Create Alarm.

  • In the Metric drop-down, select 4xx Error Rate.

  • In the Distribution drop-down, select your distribution.

  • In the Name of alarm field, provide a name for your alarm.

  • Determine if you wish to send a notification to an SNS topic and select the topic in the drop down menu.

  • Use the Whenever Sum of Requests drop down and text box to set your threshold.

  • Use the For at least text box and consecutive period(s) of drop-down to set your period.

  • Click Create Alarm.

  • Note you may also use `CloudWatch <https://console.aws.amazon.com/cloudwatch>`_ to create alarms.

CLI Remediation Steps

  • Create a CloudWatch alarm to trigger on HTTP 4xx error codes to alert when client behavior is outside your expectations.

    • aws cloudwatch put-metric-alarm --alarm-name <name> --evaluation-periods <number-of-samples> --comparison-operator <comparison-operator> --metric-name 4xxErrorRate --namespace "AWS/CloudFront" --period <evaluated-every-x> --threshold <your-expectation> --statistic <aggregated-by> --unit <unit-of-measure>

  • Similarly, create a Cloudwatch alarm to trigger on HTTP 5xx error codes when your system internal errors are outside your expectations.

    • aws cloudwatch put-metric-alarm --alarm-name <name> --evaluation-periods <number-of-samples> --comparison-operator <comparison-operator> --metric-name 5xxErrorRate --namespace "AWS/CloudFront" --period <evaluated-every-x> --threshold <your-expectation> --statistic <aggregated-by> --unit <unit-of-measure>