Cloud Storage Security: 12 Risks Businesses Should Understand

Table of Contents

1. Why cloud storage changes the risk picture
2. Risk 1: Misconfigured permissions
3. Risk 2: Data residency and jurisdiction
4. Risk 3: Insider threats
5. Risk 4: Vendor breaches
6. Risk 5: Account takeover
7. Risk 6: Sync-based malware and ransomware
8. Risk 7: Link oversharing
9. Risk 8: Retention gaps
10. Risk 9: Compliance exposure
11. Risk 10: Shadow IT
12. Risk 11: API key and token leaks
13. Risk 12: Supply chain dependencies
14. A 30-day starting plan
15. Frequently Asked Questions

Why cloud storage changes the risk picture

On-premises file servers had a simple shape. Files lived on hardware you owned, behind a firewall you managed, and access was mostly controlled by a directory service inside your network. Cloud storage removes most of that shape. NIST's definition of cloud computing in SP 800-145 describes on-demand, network-accessible resources that are rapidly provisioned, often with self-service. That is exactly what makes cloud storage useful, and exactly what makes it easy to misuse.

The security boundary moves. Your files are now reachable from any device with valid credentials, from any network, and they can be shared with anyone who has an email address or a link. The provider does real work to protect the platform: physical data centers, hardware, core software, and the operational security of the service. But the provider generally cannot know whether a folder of payroll spreadsheets should be visible to everyone in your company, or whether the person who downloaded them last Tuesday should still have access.

That split is the shared responsibility model in practice. Most of the risks below sit on the customer side of the line. They are not exotic. They are configuration, identity, process and governance problems, which means they are fixable with the same discipline you already apply to other business systems.

The twelve risks are not ranked by severity. Your exposure depends on what you store, who you work with, and where your data is subject to legal obligations. Use this list as a checklist for a first review, then score each item against your own environment.

Risk 1: Misconfigured permissions

What it is. Permissions are the most common source of cloud storage exposure. A folder is created with broad access, an admin enables a sharing setting for convenience, or a shared drive inherits permissions that nobody reviewed. The file is "secure" by the platform's standards but visible to people who should never see it.

Why it matters. Permission problems rarely look like breaches. Nobody gets an alert when a file becomes visible to a wider group. The exposure can persist for months, and it often surfaces only when someone outside the company mentions a document they should not have seen.

Mitigations.

• Define a small number of standard permission models, such as department folders, project folders and restricted finance or HR folders, and make the default for new folders the narrowest that works.
• Grant access to groups rather than individuals wherever the platform allows it, so that membership changes flow through one place.
• Remove "all staff" or domain-wide access from sensitive folders. Require a named owner for every shared drive or team space.
• Review permissions on your most sensitive folders quarterly. The step-by-step process is covered in our guide on how to audit cloud storage sharing permissions.

Risk 2: Data residency and jurisdiction

What it is. Data residency is the question of where your files are physically stored and processed. Jurisdiction is the legal regime that applies to that data, which can differ from the country where the storage is located. A file stored in one region may be subject to access requests, legal orders or contractual terms that depend on the provider's corporate structure.

Why it matters. Many businesses assume a cloud provider's region choice settles the question. It may not. Backups, support access, replication and analytics can involve other locations. For regulated data, the question is not only "where is it stored" but "who can lawfully compel access, and under what safeguards."

Mitigations.

• Ask each vendor, in writing, where primary storage, backups and support access occur. Ask which sub-processors touch the data.
• Where your sector or contracts require a specific region, confirm that the plan you are buying supports regional storage. Regional options are typically tied to particular plans and editions, so verify before you sign.
• Record the answers in your data inventory so that residency is a documented fact rather than an assumption.
• If you handle personal data from the European Economic Area, read our GDPR and cloud storage compliance guide for transfer rules and safeguards.

Risk 3: Insider threats

What it is. An insider threat is a risk created by someone who already has legitimate access. This includes malicious employees, but more often it is a well-meaning person who downloads files to a personal device, forwards a link to a personal email account, or syncs a shared folder to a laptop that is later lost.

Why it matters. Cloud storage makes bulk copying trivial. Someone leaving the company can export an entire shared drive in minutes if no controls stop them. Insider risk is also hard to detect with traditional perimeter tools, because the activity looks like normal use.

Mitigations.

• Set download and sync restrictions for sensitive folders where the platform supports them, and restrict offline access on unmanaged devices.
• Enable audit logging and review it for unusual volume, such as large downloads outside working hours or external shares created by one account in a short period.
• Build an offboarding checklist that revokes cloud access, removes the user from shared drives, and transfers ownership of their files before the account is deleted.
• Train staff on what they may and may not do with company files on personal devices. Keep the policy short and specific.

Risk 4: Vendor breaches

What it is. Your cloud provider or one of its sub-processors can suffer a security incident. The cloud provider's data center is not your data center, and you cannot inspect its controls directly. The risk is that a flaw or compromise at the vendor exposes data from many customers, including yours.

Why it matters. Vendor incidents are rare relative to the number of customers served by major platforms, but their impact can be broad. For a business, the practical questions are how quickly you would learn about an incident, what the contract requires the vendor to tell you, and what you would have to do next.

Mitigations.

• Review the vendor's independent audit reports, such as SOC 2 reports or ISO/IEC 27001 certificates, and check their scope. A certificate covering one product line does not necessarily cover every service you use.
• Use the vendor's trust or security portal to find current documentation rather than relying on sales material.
• Confirm breach notification terms in the data processing agreement and map them to your own internal escalation path.
• Where your data is highly sensitive, consider encryption that the vendor cannot read, with the trade-offs explained in our guide to zero-knowledge encryption.

Encryption helps here, but it has limits. Standard encryption at rest protects against stolen disks and some infrastructure failures. It does not protect against a compromised account or a vendor-side application flaw that operates on decrypted data. Treat encryption as one layer, not a substitute for access control.

Risk 5: Account takeover

What it is. An attacker obtains a legitimate user's password or session token, usually through phishing, credential reuse or malware, and then reads, downloads or shares files as that user. Because the activity uses valid credentials, it may pass as normal.

Why it matters. Account takeover is the most practical route into cloud storage for many attackers. A single compromised account in a shared environment can expose every file that account can reach, and a compromised administrator account can change sharing policies across the whole tenant.

Mitigations.

• Require multi-factor authentication for every account, and prioritize administrators and anyone with access to finance or HR folders. Stronger, phishing-resistant methods are preferable where available.
• Follow current identity guidance. The NIST digital identity guidelines cover authentication assurance and the use of multi-factor methods.
• Use single sign-on with a central identity provider so that you can disable access in one place.
• Set alerts for sign-ins from unfamiliar locations, new devices, or impossible travel patterns, and make sure someone is responsible for reading them.

Risk 6: Sync-based malware and ransomware

What it is. Desktop sync clients copy changes from a shared folder to every connected device. If a laptop is infected with ransomware that encrypts files on the local drive, the sync client can upload the encrypted versions to the cloud, overwriting clean copies. The attack spreads through the synchronization, not only through the network.

Why it matters. Many platforms maintain version history and deleted-file recovery, which helps. But recovery windows are finite, and a large encryption event may outpace manual restoration. The business impact is measured in lost work hours and emergency recovery effort, not only in the cost of the malware.

Mitigations.

• Keep version history enabled and know its retention window for each platform. Test a restore before you need one.
• Use endpoint protection on every device that syncs company files, and enforce operating system updates.
• Restrict sync to managed devices where the platform permits it.
• Keep a backup that is separate from the sync relationship. Sync is not backup, as the FAQ below explains.
• Plan a response that includes isolating the infected device, disabling sync for affected users, and restoring from known-good versions.

Risk 7: Link oversharing

What it is. Shareable links are designed to be easy. A link that grants access to anyone who has it can be forwarded, posted or indexed in ways the original sender never intended. Even a link that requires sign-in can expose files to external accounts if the sharing policy is permissive.

Why it matters. Link oversharing is one of the most common ways files leave the intended audience. The link itself becomes the credential, and it outlives the context in which it was created. Nobody remembers the link from a project two years ago, but it still works.

Mitigations.

• Restrict default link sharing to the organization or to specific groups. Disable "anyone with the link" for sensitive content at the tenant or domain level.
• Use link passwords and expiration dates where the platform supports them, especially for external recipients.
• Prefer sharing with named people for external collaboration, so access is visible and can be revoked by identity.
• Review existing public links on a schedule and remove those that no longer serve a purpose.

Risk 8: Retention gaps

What it is. Retention gaps happen when files are kept too long, too briefly, or in ways that do not match legal or business requirements. A file deleted after a dispute may be unrecoverable, while a file that should have been deleted under a data minimization policy may still sit in an archive.

Why it matters. Both directions cause harm. Short retention can destroy evidence, and long retention increases the amount of data exposed in any incident. Under data protection rules such as the GDPR, keeping personal data longer than necessary can itself be a compliance issue, as discussed in our GDPR guide.

Mitigations.

• Write a retention schedule that lists each category of record, how long it must be kept, and what triggers deletion.
• Apply retention and legal hold features that the platform provides, rather than relying on individuals to move files to archive folders.
• Confirm how the platform handles deleted files, including trash windows and the time after which content is purged.
• Plan deprovisioning: when a user leaves, decide whether their data is retained, transferred or deleted, and document the decision.

Risk 9: Compliance exposure

What it is. Compliance exposure is the gap between how your cloud storage is used and what the rules applicable to your business require. Examples include regulated health information, payment card data, personal data about customers or employees, and contractual confidentiality clauses that limit where data can go.

Why it matters. Compliance issues are often discovered during audits, incidents or customer due diligence, when remediation is expensive. A cloud storage deployment that was set up quickly may not meet obligations for access logging, data location, subprocessor disclosure or breach notification.

Mitigations.

• Map your obligations first. List the laws, regulations and contracts that touch the data you store, and identify which cloud folders hold each category.
• Obtain the vendor's data processing terms and check that they reflect your obligations. Confirm whether the vendor offers business associate terms or similar agreements where your sector requires them.
• Keep records of processing and access reviews that an auditor could inspect.
• Do not rely on a certification logo as proof of compliance. Ask for the report, the scope and the date.

Risk 10: Shadow IT

What it is. Shadow IT is any cloud service used without approval. Staff create accounts on personal file-sharing services, use free tiers of consumer storage for work, or connect unvetted third-party apps to company drives. The data leaves your governance without anyone deciding that it should.

Why it matters. You cannot protect what you do not know about. Shadow services often lack single sign-on, audit logs, retention and offboarding, so when someone leaves, company data remains in an account you cannot see.

Mitigations.

• Publish a short list of approved storage and sharing services, and explain why the list exists.
• Make the approved option easy to use. Shadow IT grows when the official tool is slow or missing a feature people need.
• Review OAuth grants and connected applications in your admin console. Remove apps that are not needed and restrict new app approvals to administrators.
• Ask staff what they use. The answers are usually more useful than a technical scan.

Risk 11: API key and token leaks

What it is. Many cloud storage platforms expose APIs that let scripts, backup tools and integrations read or write files. The credentials for these integrations, such as API keys, service account keys and OAuth refresh tokens, can leak through source code repositories, configuration files, logs, chat messages or screenshots.

Why it matters. A leaked integration credential may grant access without a password or multi-factor prompt, and it may persist long after the developer who created it has moved on. Automation credentials often have broad scopes because they are configured once and rarely reviewed.

Mitigations.

• Store secrets in a dedicated secrets manager, not in code or shared documents. Rotate credentials on a schedule and after staff changes.
• Grant integrations the narrowest scope that works, and prefer service accounts with documented owners.
• Scan repositories for committed secrets as part of normal development workflow.
• Inventory integrations and disable any that no longer have an owner.

Risk 12: Supply chain dependencies

What it is. Your cloud storage risk includes the software and services that connect to it: sync clients, browser extensions, backup vendors, document converters, e-signature tools and reporting platforms. Each one can have access to files and each one has its own security posture.

Why it matters. Third-party components are a frequent route into environments that are otherwise well protected. A small utility that needs read access to a shared drive may be the weakest point in the chain, particularly if it has been abandoned by its developer.

Mitigations.

• Maintain a list of every third-party application with access to company storage, with its purpose, data scope and owner.
• Apply the same vendor review to connected tools that you apply to the storage provider itself.
• Limit grants to what each application needs, and review them when the application is updated or the business process changes.
• Remove applications that are no longer in use, and make removal part of any project closeout.

A 30-day starting plan

You do not need to fix all twelve risks at once. A practical sequence for the first month looks like this.

Week 1: Inventory. List your cloud storage platforms, admin accounts, shared drives and connected applications. Identify the top five most sensitive folders.

Week 2: Access. Enforce multi-factor authentication for all users and administrators. Remove domain-wide or "anyone with the link" access from sensitive folders. Run an offboarding check on recent leavers.

Week 3: Sharing and integrations. Review external shares and public links. Revoke unused connected applications. Restrict new app approvals.

Week 4: Recovery and governance. Test a file restore from version history. Document the retention schedule and the vendor's breach notification terms. Assign an owner for each risk category, and schedule the next review.

Keep the output of each step in a shared document. An auditor, a customer or a new administrator will ask how you reached your current position, and the answer should be written down.