How should security teams control access to sensitive data in open shares?

Why This Matters for Security Teams

Open shares become dangerous when “open” means more than a temporary collaboration setting. Sensitive files, exported reports, and cached data often inherit broad group access, stale permissions, or anonymous reach that no owner is actively reviewing. That turns a storage convenience into an identity and access problem. Guidance from the OWASP Non-Human Identity Top 10 is relevant here because shared repositories are frequently accessed by service accounts, sync jobs, and automation that security teams do not see as clearly as human users. NHI Management Group notes that only 5.7% of organisations have full visibility into their service accounts in its Ultimate Guide to NHIs, which helps explain why access drift persists inside file shares.

The real issue is not whether a folder is technically shared, but whether every identity that can reach it still needs that reach. Without ownership, classification, and entitlement review, open shares quietly accumulate access from users, contractors, sync services, and legacy automation. In practice, many security teams encounter sensitive data exposure only after a downstream incident or audit finding rather than through intentional review.

How It Works in Practice

Controlling sensitive data in open shares starts with discovery, but discovery alone is not enough. Each share should be mapped to a business owner, classified by data sensitivity, and checked for the full set of identities that can reach it. That includes human users, groups, service accounts, backup tools, indexing services, and any workflow automation that reads or writes files. Where possible, tie share permissions back to an authoritative source such as an identity governance platform, not manual spreadsheets.

Security teams should then remove broad access that is not tied to a current business need and replace it with narrower groups or task-based access. For recurring workflows, current practice increasingly favors just-in-time elevation and short-lived access over standing permissions, especially when open shares contain regulated or highly sensitive content. This aligns with Zero Trust thinking: verify identity, context, and purpose at request time rather than assuming anyone inside the network or on the file server is safe. NHI Management Group’s Ultimate Guide to NHIs — Key Challenges and Risks highlights how excessive privileges and weak visibility amplify exposure across identity estates, and the same pattern appears in file-share access reviews.

• Classify the content first, then set access rules from the classification level.
• Review group membership, inherited permissions, and anonymous link settings together.
• Identify non-human readers such as backup jobs, ETL pipelines, and sync agents.
• Replace shared folder access with case-specific access where business operations allow it.
• Log access events and make remediation part of the entitlement review cycle.

For implementation detail, the OWASP Non-Human Identity Top 10 is useful for framing service-account and automation access, while the NHI lifecycle guidance in Ultimate Guide to NHIs — Standards supports a more disciplined review and offboarding model. These controls tend to break down when open shares are embedded in legacy workflows because permissions changes can interrupt reporting, backups, and line-of-business integrations.

Common Variations and Edge Cases

Tighter share control often increases operational overhead, requiring organisations to balance faster collaboration against tighter entitlement governance. That tradeoff is real, especially in engineering, finance, and analytics teams that depend on shared folders for batch jobs, exports, and ad hoc review. Current guidance suggests that “everyone in the department” access is rarely defensible for sensitive data, but there is no universal standard for every collaboration model, so exception handling must be explicit and time-bound.

One common edge case is data that must remain broadly readable for operational reasons, such as dashboards or shared reference material. In those environments, security teams should separate read-only operational copies from source data and restrict the source more tightly. Another case is automation that scans or moves files on behalf of users. Those identities should be treated as NHIs with named ownership, scoped permissions, and regular review, not as invisible infrastructure. NHI Management Group’s research shows that broad identity exposure and weak visibility are recurring patterns in compromise scenarios, including in the 52 NHI Breaches Analysis.

Where teams struggle most is in environments with inherited permissions, nested groups, or file shares that have been live for years without an owner. In those cases, the correct response is usually not to lock everything down at once, but to create a remediation queue, prioritise by sensitivity, and remove access in stages with business sign-off.

Related resources from NHI Mgmt Group

• How should security teams prepare data access governance before enabling GenAI tools?
• How should security teams run access reviews for non-human identities?
• How should security teams govern non-human identities that have persistent access?
• How should security teams govern API keys used for generative AI access?