Why do publicly accessible storage buckets remain a recurring risk in cloud environments?

Why This Matters for Security Teams

Public bucket exposure is still a recurring problem because cloud storage is easy to provision, easy to forget, and often managed outside the normal identity and change-control lifecycle. The issue is not just “open to the internet” settings. It is also ownership drift, inherited permissions, and copied configurations that outlive the workload they were meant to support. Guidance in NIST Cybersecurity Framework 2.0 and NHIMG’s Ultimate Guide to NHIs both point to the same operational reality: exposure often survives because no system is continuously accountable for it.

The security impact is straightforward. An exposed bucket can leak application data, backups, logs, software artifacts, or secrets embedded in files. Once content is reachable, attackers do not need a complex intrusion path. They can enumerate objects, harvest metadata, and use the bucket as a pivot point for lateral movement or credential abuse. In practice, many security teams encounter public storage not through planned review, but after external discovery, incident response, or a third-party report.

How It Works in Practice

Most organisations do not intentionally create risky buckets; the exposure appears through routine cloud operations. A developer sets a permissive policy for testing, a migration script copies an old ACL, or a platform team grants broad access to speed up delivery. Over time, those temporary choices become persistent because ownership is unclear and the bucket is not tied to a tight review cycle. That is why cloud storage risk is often a governance problem as much as a technical one.

The practical control pattern is layered. First, make public access a denied-by-default posture and use policy guardrails to stop accidental exposure before it is deployed. Second, treat every bucket as a managed asset with a named owner, business purpose, and expiry review. Third, continuously detect drift so internet exposure, anonymous read access, and overly broad cross-account permissions are flagged quickly. NIST control families in SP 800-53 Rev. 5 support this approach through access control, configuration management, and continuous monitoring.

NHIMG’s 52 NHI Breaches Analysis and the Microsoft SAS Key Breach both reinforce a recurring pattern: storage exposure rarely stays isolated. Public access can reveal tokens, connection strings, or operational data that let an attacker move from passive discovery to active compromise. These controls tend to break down in multi-account environments where bucket creation is decentralised and asset ownership is not enforced consistently.

• Use organisation-level guardrails to block anonymous access unless there is an explicit, time-bound exception.
• Require classification and owner assignment at bucket creation, not after deployment.
• Scan for public ACLs, bucket policies, and object-level exceptions continuously, not only during audits.
• Remove secrets from stored objects and logs so an exposed bucket does not become a credentials incident.

Common Variations and Edge Cases

Tighter storage controls often increase operational overhead, requiring organisations to balance speed of delivery against the cost of review and remediation. That tradeoff is manageable, but only if exceptions are visible and temporary. Current guidance suggests that “public” should not be treated as a binary label alone. Some buckets are intentionally internet-facing for content delivery or open datasets, but those cases need narrowly scoped policies, object integrity controls, and frequent validation.

There is no universal standard for this yet, especially across hybrid and multi-cloud estates. Some teams rely on native cloud logging, while others add configuration posture tools or policy-as-code layers. The right mix depends on whether the bucket stores production data, build artifacts, user uploads, or support exports. A bucket that only hosts static website assets may tolerate broader exposure than one containing backups or telemetry, but both still require explicit ownership and review. NHIMG’s 2024 Non-Human Identity Security Report notes that Top 10 NHI Issues remain concentrated around weak access governance and inconsistent operational control.

The hardest edge case is legacy storage that has accreted permissions over years. Those buckets often sit outside current infrastructure-as-code pipelines, which makes them easy to miss and slow to retire. In those environments, the practical answer is a staged cleanup campaign, not a one-time policy change.

Related resources from NHI Mgmt Group

• Why do publicly accessible S3 buckets create compliance and breach risk for organisations?
• Why do cloud storage environments increase the risk of PCI data exposure even when encryption is enabled?
• How should security teams reduce insider threat risk in cloud environments?
• Why do cloud environments increase non-human identity risk?