Secure Cloud Storage and File Sharing
Keep cloud files safer by encrypting sensitive data in transit and at rest where possible, restricting sharing permissions, and avoiding accidental public exposure or unsafe document disclosure.
Cloud storage is convenient, but misconfigured shares and accidental exposure are common failure modes. The highest risk is "public by mistake" links or overshared folders. This guide is for UK users and small organisations using common cloud sync and sharing, translating ICO disclosure guidance and joint U.S. government cloud guidance into practical controls.
Safer sharing defaults
- Prefer named users over "anyone with the link".
- Use least privilege and time-limited access where available.
- Remove hidden personal info before sharing documents.
Cloud storage risks that matter most
Public exposure, over-permissive links, and weak sharing hygiene are the main risks. NSA/CISA guidance warns that object storage is commonly exploited due to misconfiguration and stresses auditing for public exposure. Encryption in transit and at rest (TLS 1.2+) is imperative for sensitive cloud data.
Safer sharing defaults
- Named users: Share with specific people rather than "anyone with the link".
- Least privilege: Grant only the access needed (view vs edit).
- Time-limited access: Use expiry where the service supports it.
Encryption basics for shared files
Encryption in transit (e.g. TLS) and at rest helps protect sensitive data. It does not solve permission mistakes—you can still share with the wrong people. Ensure your provider uses encryption; check their documentation.
Avoid accidental disclosure
ICO guidance focuses on preventing accidental personal information breaches when disclosing documents. Reduce data to what's necessary, remove hidden personal info (metadata, track changes, comments), and double-check recipients and permissions before sending.
Auditing and clean-up
Review links and shares regularly. Revoke stale access. Monitor for unusual access patterns. NCSC discusses using built-in cloud services safely.
If you shared something by mistake
Contain: revoke the link or share immediately. Document what was shared and with whom. Notify relevant parties if personal data was exposed. Consider whether you need to report a breach under UK GDPR.
Frequently asked questions
- Why are "anyone with the link" shares risky?
- They can be forwarded or discovered; you lose control of who accesses the file.
- Does encryption solve cloud sharing risk?
- It helps protect data, but permission mistakes can still expose content to the wrong people.
- What's the safest first step before sharing a document?
- Reduce the data to what's necessary, remove hidden personal info, and double-check recipients and permissions.