I keep running into questions that force me to balance security and cost as a cloud security engineer while preparing for the AWS Certified Security – Specialty (SCS) exam.

One question that stood out to me is:

Should I enable GuardDuty in all AWS regions—even the ones I don’t actively use?

At first glance, it feels like a trade-off between cost efficiency and security coverage. But after digging deeper, the answer becomes clearer.

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Security Best Practice: Enable GuardDuty Everywhere

From a security perspective, AWS makes the recommendation simple: enable GuardDuty in every region.

• Attackers don’t care about “active” vs. “unused” regions. If credentials are compromised, they can spin up resources anywhere.
• Blind spots create risk. Without GuardDuty, malicious activity in an unused region might never trigger an alert.
• Best practice and compliance: Both the AWS Well-Architected Framework and major compliance standards call for region-wide GuardDuty coverage.

For the SCS exam, when the question is about best practices, the correct answer is always: enable GuardDuty in all regions.

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The Cost Question

But what about the cost?

Yes, GuardDuty is billed per region based on the amount of data analyzed:

• In active regions, I pay the expected charges for analyzing VPC Flow Logs, DNS logs, CloudTrail, and EKS audit logs.
• In unused regions, little or no activity means the cost is close to zero.

So while enabling GuardDuty globally technically means more coverage, the financial impact in unused regions is minimal.

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Balancing Security and Cost

Here’s how I approach it:

• As a security engineer, my top priority is coverage over cost savings.
• Full regional visibility ensures there are no blind spots for attackers to exploit.
• The additional spend in unused regions is negligible compared to the risk of missing a threat.

This is one of those rare cases where best practice and cost efficiency align.

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Conclusion

For both exam scenarios and real-world operations, my takeaway is clear:

✅ Enable GuardDuty in all AWS regions.

I gain consistent visibility, prevent blind spots, and align with AWS best practices—all without significant added cost.

When the choice is between security coverage and cost savings, I know which side wins: security comes first.

And this isn’t just about GuardDuty. It’s the same with CloudTrail: it should be enabled globally, across all regions. Not only for the exam, but also for real-world security operations. That’s how we eliminate blind spots and maintain full accountability across AWS.

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🔥 Pro Tip: I use AWS Organizations with Security Hub to centralize GuardDuty and CloudTrail findings across accounts and regions. This keeps monitoring simple while ensuring I don’t compromise on coverage.

Created By Yao Zhang Using ChatGPT.