Cloud & Container Security · beginner · ~10 min

Storage buckets, security groups, and public exposure

Recognise the classic public-exposure misconfigurations.

Overview

The top cloud findings are accidental public exposure: storage buckets made public (data/secrets leak), and security groups opening SSH/RDP/databases to 0.0.0.0/0. Plus public snapshots, databases, and dashboards. Fix: default-deny, block public access, restrict source ranges, no secrets in buckets.

Why it matters

Public buckets and 0.0.0.0/0 rules are among the most common and damaging cloud breaches — direct data exposure or internet-facing admin access with no exploit. They're quick to find and high impact.

Core concepts

Public buckets. Private by default, often misconfigured public; name enumeration. Security groups. Avoid 0.0.0.0/0 on 22/3389/DB ports. Other. Public snapshots/AMIs/dashboards/DBs. Fix. Block public access, least-privilege policies, restricted source ranges, bastions/VPN.

Lesson

The most common cloud findings are resources accidentally exposed to the internet.

Public storage buckets

Object storage (S3, Azure Blob, GCS) is private by default but frequently made public by mistake — a checkbox, a broad bucket policy, or ACLs granting AllUsers. Result: customer data, backups, and secrets readable by anyone who knows (or guesses) the bucket name. Bucket-name enumeration is routine recon. The fix: block public access at the account level, least-privilege bucket policies, and don't store secrets in buckets.

Security groups / firewall rules

Cloud security groups are virtual firewalls on instances. The classic mistake is opening sensitive ports to 0.0.0.0/0 (the whole internet) — SSH (22), RDP (3389), databases (3306/5432), or admin panels exposed globally. The fix: restrict source ranges, use bastions/VPN, and default-deny inbound.

Other exposed surfaces

Public snapshots/AMIs, public databases, unauthenticated dashboards (Kibana, etc.), and management APIs left open.

Testing

Enumerate the account's resources and ask, for each: is this reachable from the internet, and should it be? Public exposure + weak/no auth is a direct breach, no exploit required.

Summary

Cloud's classic breaches are public storage buckets and over-open security groups exposing sensitive ports to the whole internet. Default-deny, account-level public-access blocks, restricted source ranges, and keeping secrets out of buckets are the fixes.

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