Amazon GuardDuty provides continuous threat detection for compromised instances by analyzing VPC Flow Logs, DNS logs, and CloudTrail events. According to AWS Certified Security - Specialty guidance, GuardDuty is the fastest service to enable for detecting malware and compromised EC2 instances.
To notify the security team, Amazon SNS provides a native email notification mechanism with minimal setup. Amazon EventBridge integrates directly with GuardDuty findings and can filter based on severity.
Creating an EventBridge rule that matches high severity GuardDuty findings and publishes to SNS ensures immediate notification.
Security Hub is not required for this use case and adds additional setup time. Amazon SQS does not support email subscriptions.
Referenced AWS Specialty Documents:
AWS Certified Security - Specialty Official Study Guide
Amazon GuardDuty Findings and Severity
Amazon EventBridge Integration with GuardDuty

The fastest, least-effort way to mitigate SQL injection at the edge-without modifying legacy application code-is to place the application behind a component that supportsAWS WAFand applymanaged SQL injection protections. AnApplication Load Balancerintegrates directly with AWS WAF, allowing the security engineer to deploy a web ACL (including AWS Managed Rules for SQL injection and custom patterns based on the provided samples) and immediately start blocking malicious payloads before they reach the EC2 instances and the database.
Option A also preserves normal operations during rollout: you can create the ALB, register the existing EC2 instances as targets, validate health checks and traffic behavior, apply WAF protections, and then shift Route
53 weighted records to the ALB with minimal downtime. Finally, tightening the EC2 security groups to prevent direct internet access ensures all inbound web traffic is forced through the ALB + WAF inspection point, reducing exposure quickly.
Option B is risky because it uses only one EC2 origin (reducing availability) and adds CloudFront origin configuration complexity under a 24-hour deadline. Option C requires code changes on unsupported software and is unlikely to be safely delivered in time. Option D is invalid because AWS WAF cannot be attached directly to EC2 instances, and changing DB-port exposure doesn't address SQL injection on the web layer.

AWS KMS enforces amandatory minimum waiting period of 7 daysbefore a customer managed key can be deleted. According to AWS Certified Security - Specialty incident response guidance,no method exists to immediately delete a KMS key. The fastest possible deletion is achieved by scheduling deletion with the minimum 7-day waiting period.
In this scenario, although deletion was previously scheduled, the key remains enabled and usable. The most authoritative and reliable method to regain control and reissue deletion immediately is touse the AWS account root user, which has implicit permissions to manage KMS keys regardless of compromised IAM principals.
Option B is incorrect because KMS keys are regional resources; multi-Region keys require coordinated deletion but do not shorten the waiting period. Option C is unnecessary because the key policy already allows kms:*. Option D increases the deletion waiting period to 30 days, which violates the requirement to delete the key as quickly as possible.
AWS documentation clearly states thatroot user access is the ultimate authority for KMS key management and that7 days is the minimum deletion window, making this the fastest valid option.
* AWS Certified Security - Specialty Official Study Guide
* AWS Key Management Service Developer Guide
* AWS Incident Response Best Practices

CloudTrail trails can be configured as eithersingle-Regionormulti-Region. A single-Region trail delivers events only for the Region in which it is created; when the company begins using additional Regions, those events will not be logged to the existing S3 destination unless the trail is updated. The least operational overhead is tomodify the existing trailand enablemulti-Regionlogging (that is, configure the trail to "apply to all Regions"). This preserves the current S3 bucket destination, encryption settings, log file validation configuration, IAM roles, and any integrations that already depend on the existing trail name and S3 prefix structure.
Creating a new trail (Options A or C) increases overhead because the engineer would need to manage multiple trails or migrate downstream processes (alerting, Athena tables, SIEM ingestion, retention policies, and lifecycle rules). Option B is not how CloudTrail works-S3 notifications do not cause CloudTrail to collect events from other Regions; CloudTrail must be configured to generate and deliver those logs.
Therefore, updating the existing trail to be multi-Region is the simplest and most maintainable fix.

Amazon S3 Lifecycle configuration rules are the native, automated mechanism for managing object retention and deletion. According to AWS Certified Security - Specialty documentation, lifecycle rules can be configured to expire objects based on the number of days since object creation. Once the expiration time is reached, Amazon S3 permanently deletes the objects without manual intervention.
This solution directly enforces a maximum retention period of 72 hours and ensures compliance regardless of whether the vendor downloads the data or not. Lifecycle rules are evaluated continuously by Amazon S3 and do not require scripts, cron jobs, or additional services, making them the most operationally efficient and cost- effective solution.
S3 Versioning controls versions but does not enforce object deletion timelines. S3 Intelligent-Tiering optimizes storage cost but does not delete objects. Presigned URLs only control access duration and do not remove objects from storage.
AWS explicitly recommends lifecycle policies for automated data retention enforcement.
Referenced AWS Specialty Documents:
AWS Certified Security - Specialty Official Study Guide
Amazon S3 Lifecycle Management