Implementing an Automated Solution for Updating Amazon VPC NACLs

Correct Answer: B.

For an automated preventive action based upon Amazon GuardDuty findings, Amazon CloudWatch Events and Amazon Lambda function can be used.

Amazon GuardDuty findings are sent to Amazon CloudWatch events based upon match criteria, triggers an AWS Lambda function which will modify VPC NACLs based upon Amazon GuardDuty findings.

Option A is incorrect as the CloudWatch alarm cannot be used to trigger a Lambda function directly.

Option C is incorrect as using a cron job will result in additional admin work.

Option D is incorrect as using a cron job will result in additional admin work.

For more information on Amazon GuardDuty, refer to the following URL,

https://aws.amazon.com/blogs/security/how-to-use-amazon-guardduty-and-aws-web-application-firewall-to-automatically-block-suspicious-hosts

The scenario in this question involves a Start-up firm that has critical application servers deployed in an Amazon VPC, with Amazon GuardDuty enabled for additional security. The management of the firm is looking for an automated solution to update Amazon VPC NACLs in response to malicious activity findings by Amazon GuardDuty. The question asks which of the given options can be implemented with the least effort.

Option A suggests creating an Amazon CloudWatch alarm based on GuardDuty findings that triggers an AWS Lambda function to update NACLs. This option leverages the event-driven architecture of AWS Lambda and uses GuardDuty findings as the event trigger to update the NACLs. This approach involves creating a CloudWatch alarm that monitors GuardDuty findings and invokes a Lambda function that updates the NACLs. This option is an efficient and automated approach to respond to malicious activities findings by GuardDuty, but it requires the creation of a Lambda function to update the NACLs.

Option B suggests creating an Amazon CloudWatch events rule based on GuardDuty findings that triggers an AWS Lambda function to update NACLs. This option also leverages the event-driven architecture of AWS Lambda and uses GuardDuty findings as the event trigger to update the NACLs. This approach involves creating a CloudWatch events rule that monitors GuardDuty findings and invokes a Lambda function that updates the NACLs. This option is similar to Option A but uses CloudWatch events rules instead of CloudWatch alarms. CloudWatch events rules are more flexible and offer more options to filter and route events, but they require more configuration compared to CloudWatch alarms.

Option C suggests creating an Amazon CloudWatch events rule based on GuardDuty findings that triggers a cron job to update NACLs. This option also uses GuardDuty findings as the event trigger to update the NACLs but uses a cron job instead of a Lambda function. This approach involves creating a CloudWatch events rule that monitors GuardDuty findings and invokes a cron job that updates the NACLs. This option is not as efficient and automated as Options A and B because it relies on a cron job to update the NACLs, which requires additional configuration and maintenance.

Option D suggests creating an Amazon CloudWatch alarm based on GuardDuty findings that triggers a cron job to update NACLs. This option uses a similar approach to Option C but uses a CloudWatch alarm instead of a CloudWatch events rule to monitor GuardDuty findings. This option is the least automated and efficient among the given options because it relies on a cron job to update the NACLs and requires the creation of a CloudWatch alarm to monitor GuardDuty findings.

In conclusion, the most efficient and automated approach to meet the requirement of updating Amazon VPC NACLs in response to malicious activities findings by Amazon GuardDuty is Option A, which involves creating an Amazon CloudWatch alarm that triggers an AWS Lambda function to update NACLs. This option uses the event-driven architecture of AWS Lambda and offers the most efficient and automated solution among the given options.