Misconfigurations remain the top cause of cloud security incidents. While AWS has improved defaults over the years, many organizations still leave critical gaps open to attackers.

This guide outlines five high-impact AWS security misconfigurations, explains why they matter, and shows how to fix them with both Console and Terraform examples. These are based on real-world findings from security audits in 2024–2025.

1. Public S3 Buckets

Despite stronger AWS defaults, public S3 buckets continue to expose sensitive data.

Why It Matters

  • Public objects can be discovered via brute force or Google indexing.
  • Attackers use open buckets for staging malware or stealing PII.

How to Fix It

AWS Console:

  • Go to S3 > Block Public Access settings for this account
  • Enable all four options at the account level.
  • Account level restrictions will override object level restrictions.

Terraform:

resource "aws_s3_account_public_access_block" "global" {
  block_public_acls       = true
  block_public_policy     = true
  ignore_public_acls      = true
  restrict_public_buckets = true
}

Tooling Tip:
Use Access Analyzer for S3 to identify any buckets with public access.

2. Overly Permissive IAM Policies

Too often, IAM policies grant Action: * or Resource: * access—even for automation or dev roles.

Want to fix IAM permissions more precisely?
Check out Building Least-Privilege IAM Roles with IAM Access Analyzer — with CLI examples and Terraform.

Why It Matters

  • Violates least privilege.
  • Increases blast radius of compromised credentials.

How to Fix It

Audit Existing Policies:

aws iam simulate-custom-policy   --policy-input-list file://policy.json   --action-names "s3:GetObject" "ec2:TerminateInstances"

Use Permission Boundaries or Access Analyzer:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": ["s3:GetObject"],
      "Resource": ["arn:aws:s3:::my-secure-bucket/*"]
    }
  ]
}

Pro Tip:
Use IAM Access Analyzer to generate least-privilege policies from actual usage.

3. IAM Users Without MFA (or Still Using IAM Users at All)

IAM users should no longer be used for human access in 2025.

Why It Matters

  • IAM users with static access keys are easy targets.
  • No central lifecycle management (unlike SSO).

What to Do Instead

  • Adopt IAM Identity Center (SSO) with your identity provider.
  • Use STS AssumeRole for temporary access in automation.
  • For legacy systems:
    • Enforce MFA
    • Monitor with AWS Config + CloudTrail

Example MFA Enforcement Policy:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Deny",
      "Action": "*",
      "Resource": "*",
      "Condition": {
        "BoolIfExists": { "aws:MultiFactorAuthPresent": "false" }
      }
    }
  ]
}

4. Security Groups Open to the World

Security groups allowing 0.0.0.0/0 on port 22 or 3389 remain common and dangerous.

Why It Matters

  • These ports are constantly scanned.
  • Exploits against SSH/RDP services are common.

How to Fix It

Recommended:
Use AWS Systems Manager Session Manager for shell access (no open ports required).

5. Insufficient Logging and Monitoring

Logging is essential for investigation, compliance, and threat detection.

Must-Have Services

  1. AWS CloudTrail (multi-region, org-wide)
  2. AWS Config
  3. Amazon GuardDuty
  4. AWS Security Hub

By leveraging services like AWS CloudTrail, AWS Config, Amazon GuardDuty, and AWS Security Hub, organizations can establish a comprehensive security framework in AWS. Together, these tools provide detailed visibility into API activity, ensure continuous compliance with best practices, detect threats using intelligent analysis, and centralize security findings for actionable insights. This integrated approach enhances your ability to prevent, detect, and respond to security incidents effectively, while maintaining a strong security posture across your AWS environment.

Cost Tip:
Set retention on CloudWatch logs to avoid unnecessary spend.

📄 Need a full checklist to audit your environment?
Read the AWS Security Checklist 2025 — 10 critical steps, all in one post.

Final Thoughts

Misconfigurations like these are often easy to fix—but also easy to miss.

By tackling these five areas, you significantly reduce the likelihood of breaches, increase visibility, and build a security-first cloud foundation.

Coming up: deeper dives into automation, policy generation, and detection workflows in AWS.

📄 Handling misconfigurations is one thing. Responding to them fast is another. Check out the AWS Incident Response Playbook →

Cloud security isn’t just about avoiding breaches—it’s about building resilient, auditable systems. These fixes are a strong start.