An audit determined that a company's Amazon EC2 instance security group violated company policy by...

The most operationally efficient solution to implement a near-real-time monitoring and alerting solution that will notify administrators of security group violations is to use the restricted-ssh AWS Config managed rule that is invoked by security group configuration changes that are not compliant. This rule checks whether security groups that are in use have inbound rules that allow unrestricted SSH traffic. If a violation is detected, AWS Config can use the remediation feature to publish a message to an Amazon Simple Notification Service (Amazon SNS) topic.

Option A is incorrect because creating a recurring Amazon Inspector assessment run that uses the Network Reachability package is not operationally efficient, as it requires setting up an assessment target and template, running the assessment every day, and invoking a Lambda function to retrieve and evaluate the assessment report. It also does not provide near-real-time monitoring and alerting, as it depends on the frequency and duration of the assessment run.

Option C is incorrect because configuring VPC Flow Logs for the VPC and specifying an Amazon CloudWatch Logs group is not operationally efficient, as it requires creating a log group and stream, enabling VPC Flow Logs for each subnet or network interface, and subscribing a Lambda function to parse and analyze the log entries. It also does not provide proactive monitoring and alerting, as it only detects successful connections on port 22 after they have occurred.

Option D is incorrect because creating a recurring Amazon Inspector assessment run that uses the Security Best Practices package is not operationally efficient, for the same reasons as option A. It also does not provide specific monitoring and alerting for security group violations, as it covers a broader range of security issues. References:

[AWS Config Rules]

[AWS Config Remediation]

[Amazon Inspector]

[VPC Flow Logs]