Document-Level Security

DLS operates on a binary principle: a user either has access to a document or they do not. This is enforced by binding a user identity or group membership directly to an Access Control List (ACL) on the document object. Unlike field-level security, which masks specific data points, DLS treats the document as an atomic unit of protection. In a RAG pipeline, this means the document is completely excluded from the semantic index or filtered out during pre-retrieval filtering, making it impossible for the LLM to ground an answer on it.

In modern AI architectures, DLS is enforced at the retrieval stage, not the generation stage. This is critical for Retrieval-Augmented Generation Authorization. The two primary methods are:

• Pre-Retrieval Filtering: The user's security credentials are passed to the vector database query. The search is scoped to only those document chunks whose parent document ACL includes the user. This is the most secure and performant method.
• Post-Retrieval Filtering: The query runs broadly, and then results are security trimmed to remove unauthorized documents. This is less efficient and risks leaking metadata or document counts.

DLS is a specific implementation of broader access control paradigms. It is most commonly implemented using:

• Role-Based Access Control (RBAC): Access is granted based on a user's role (e.g., 'HR Manager' can see all HR documents).
• Attribute-Based Access Control (ABAC): Access is evaluated dynamically based on user attributes (e.g., department, clearance level), resource attributes (e.g., classification tag), and environmental context. DLS is the enforcement point for these policies on unstructured content, translating a logical policy into a binary retrieval decision.

Security trimming is the operational process that enforces DLS. It is the act of removing non-permitted results from a result set. A common anti-pattern is to rely solely on post-retrieval trimming in a RAG system. If a search returns 100 chunks but the user can only see 10, the context window for the LLM is starved of relevant information, leading to a poor or hallucinated answer. Effective DLS requires the security filter to be pushed down to the index query itself.

Document-Level Security is a fundamental enforcement point for a Zero Trust Architecture (ZTA). The principle of 'never trust, always verify' requires continuous authorization at the data layer. DLS ensures that even if a network perimeter is breached or a service account is compromised, the attacker cannot exfiltrate a mass of documents. Every single document retrieval attempt is independently authorized against the user's current, continuously validated identity, adhering to the Least Privilege Principle.

The process of filtering search or retrieval results to exclude content that the querying user does not have permission to see. In a vector search pipeline, security trimming can occur at two stages:

• Pre-retrieval filtering: User permissions are applied as a filter before the query executes, ensuring only authorized documents are scored.
• Post-retrieval filtering: The query runs broadly, and results are subsequently filtered to remove unauthorized documents before presentation. Pre-retrieval filtering is preferred for performance, but post-retrieval may be necessary when permission logic is too complex for index-time enforcement.

A security configuration that restricts access to specific data fields within a larger record or document. While document-level security controls entire documents, field-level security allows partial access. For example, a user may be authorized to see a contract's summary but not its financial terms. In retrieval systems, this requires dynamic data masking or redaction of sensitive fields before the document is returned to the user or passed to the language model for synthesis.