🛡️ Building a CASB‑Like Threat Monitoring Lab in AWS (Beginner Friendly)

Source: Dev.to

📌 Project Sequence

• Part 1: AWS IAM Hardening — strengthening identity boundaries and improving authentication hygiene
• Part 2: Cloud Security Posture Management (CSPM) using Security Hub + AWS Config
• Part 3: CASB‑Like Monitoring with GuardDuty + CloudTrail — real‑time detection, safe anomaly generation, delegated‑administrator behavior, and AWS threat‑intelligence findings

🔐 Why This Progression Matters

Modern cloud‑security teams protect environments in layers:

Identity first → Posture second → Threat detection next

Project 3 adds behavioral visibility, anomaly detection, and event‑driven alerts—core fundamentals for SOC analysts, detection engineers, threat hunters, and cloud‑security specialists.
The lab simulates a lightweight Cloud Access Security Broker (CASB) workflow using native AWS services.

Table of Contents

• Introduction
• What You Will Build
• Prerequisites
• Step 1 — Enable CloudTrail With Secure Settings
• Step 2 — Enable GuardDuty (Threat Detection)
• Step 3 — Generate Safe Test Activity
• Step 4 — Review GuardDuty Findings
• Step 5 --- Cleanup to Avoid Costs
• Final Thoughts
• Connect

Introduction

Cloud‑security monitoring doesn’t have to be complicated, and you don’t need enterprise‑grade CASB tools to begin learning how threat detection works in the cloud.

This beginner‑friendly lab shows how to simulate CASB‑like monitoring using AWS CloudTrail + GuardDuty, while keeping everything free or extremely low‑cost. You’ll generate safe test activity, view detections, and learn how these services help security teams identify risky behavior inside AWS environments.

The guide also includes troubleshooting notes (manual KMS encryption, delegated‑admin restrictions, etc.) so beginners know what to expect.

What You Will Build

• CloudTrail logging your AWS API activity
• GuardDuty analyzing those logs for threats
• Sample findings plus real findings from safe test events
• A lightweight, CASB‑like monitoring workflow
• A clean environment with no ongoing costs

Prerequisites

• An AWS account
• An IAM user or role with admin‑level permissions
• A single region chosen for the lab (recommended: us-east-1)
• (Optional) AWS CLI installed

Step 1 — Enable CloudTrail With Secure Settings

CloudTrail records API activity across your AWS account. It’s the backbone for detection and threat monitoring.

✅ Create a CloudTrail Trail

1. Open CloudTrail → Trails → Create trail.

2. Name your trail exactly:

   casb-guardduty-lab-trail

3. Create a new S3 bucket for log storage.

4. Manually enable the following options:

   • SSE‑KMS encryption (use the AWS‑managed key)
   • Log file validation

Tip: Many beginners miss these settings—CloudTrail does not always enable SSE‑KMS or validation by default, depending on the UI version. Enabling them adds integrity and confidentiality protections to your logs.

Step 2 — Enable GuardDuty (Threat Detection)

GuardDuty continuously analyzes CloudTrail logs, VPC Flow Logs, and DNS logs for suspicious or malicious activity.

✅ Enable GuardDuty

1. Open GuardDuty in the console.
2. Click Enable GuardDuty.
3. If GuardDuty creates a Delegated Administrator, note the account ID for later cleanup.

Step 3 — Generate Safe Test Activity

🔹 Option A – Generate AWS Sample Findings

1. In GuardDuty, open the Actions menu.
2. Choose Generate sample findings.

These simulated attacks let you practice incident triage.

🔹 Option B – Create Real‑World Test Events

1. Console Login Events

• Log out and back into the AWS console.
• Create a test IAM user and intentionally fail login attempts.

These appear as ConsoleLogin events in CloudTrail.

2. Activity From an Unusual Region

• Switch from your home region to eu‑west‑1 or ap‑southeast‑1.
• Open services or start to create resources (cancel before provisioning).

CloudTrail logs these actions with the region included.

3. Simple CLI Call (Optional)

aws ec2 describe-instances --region us-east-1

or create a temporary IAM user and attempt a privileged API call. GuardDuty will flag the activity (e.g., “UnauthorizedAccess:RootLogin”).

Warning: Only run test actions in a non‑production account. Delete any resources you create afterward.

Step 4 — Review GuardDuty Findings

1. Navigate to GuardDuty → Findings.
2. You’ll see both the sample findings and any real findings generated by your test activity.

Example Findings

• UnauthorizedAccess:IAMUser/ConsoleLogin – suspicious console login attempts.
• Recon:EC2/PortProbe – scanning activity against EC2 instances.
• AnomalousBehavior – unusual login locations or regions.

Each finding includes severity, affected resource, and recommended remediation steps. Use these details to map back to the underlying CloudTrail events—this is the core of a threat‑investigation workflow.

Step 5 --- Cleanup to Avoid Costs

1. Remove Delegated Administrator (if any)

• Open GuardDuty → Settings → Accounts.
• Click Disable delegated administrator and confirm.

2. Disable GuardDuty

• GuardDuty → Settings → Disable GuardDuty (or disable in each region).

3. Delete the CloudTrail Trail

• CloudTrail → Trails → select your trail → Delete.

4. Delete the S3 Bucket

• Empty the bucket, then delete it.

5. Remove Test Resources

• Delete any IAM users, roles, or other resources created in Option B.

Ensuring these steps are completed prevents any lingering charges.

Final Thoughts

• This lab demonstrates how a CASB‑like monitoring capability can be built entirely with native AWS services.
• The combination of CloudTrail (immutable log source) and GuardDuty (managed threat detection) provides a solid foundation for any cloud‑security program.
• By generating safe test activity, you gain hands‑on experience with the full detection‑to‑response lifecycle without risking production workloads.

Feel free to extend the lab—add VPC Flow Logs, enable additional GuardDuty detectors, or integrate findings with Security Hub for centralized alerting. Happy hunting!

Connect

If you enjoyed this article or are learning DevOps, Linux, Security, or Cloud automation, I’d love to connect, share ideas, and learn together.

👉 LinkedIn