Policy-Based Write Filter for Windows Protected Volume Security
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing Windows Embedded systems with file-based write filters can be vulnerable to malicious modifications due to exclusion list backdoors, allowing unintended changes to protected volumes despite the intention to prevent runtime modifications.
Innovation Solution
Implementing a policy-based write filter positioned below the file-based write filter to evaluate and block or allow write requests based on defined policies, ensuring that only authorized modifications are permitted on protected volumes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a file-based write filter is used to prevent modifications to protected volumes, then the integrity of the operating system image is improved, but the ability to allow legitimate file modifications through exclusion lists creates a security vulnerability
Solution Approach 1:
A policy-based write filter is introduced as an intermediary component between the file-based write filter and the protected volume. This intermediary evaluates write requests against defined policies before allowing them to reach the exclusion list mechanism, thereby mediating between the need for OS image protection and the risk of backdoor exploitation. The policy-based filter acts as a security gatekeeper that can identify and block malicious exclusion list operations while permitting legitimate file modifications.
2Adaptability or versatility
If exclusion lists are implemented to allow certain files to be modified, then the versatility of the write filter system is improved, but the risk of malicious code exploitation increases
Solution Approach 1:
The system implements feedback mechanisms where write requests are evaluated against policies that consider the source, destination, and nature of the modification. The policy-based write filter provides feedback control by continuously monitoring write operations and comparing them against predefined security policies, allowing the system to adaptively permit or block modifications based on real-time analysis rather than static exclusion lists. This feedback loop prevents malicious exploitation while maintaining necessary versatility.
3Reliability
If the file-based write filter redirects all writes to overlay, then the protection of the protected volume is improved, but the ability to perform legitimate updates is reduced
Solution Approach 1:
The system transitions from a static write redirection approach to a dynamic policy-based evaluation system. Instead of uniformly redirecting all writes to overlay or allowing modifications based on static exclusion lists, the policy-based write filter dynamically evaluates each write request against current policies, user credentials, application context, and file attributes. This dynamic approach enables the system to flexibly permit legitimate updates while maintaining protection against unauthorized modifications, resolving the contradiction between over-protection and operational flexibility.
Data Source
AI summary
Applications and users can be restricted from making persistent changes to artifacts on a protected volume. In Windows-based systems that include a file-based write filter, a policy-based write filter can be positioned below the file-based write filter and can examine any write requests that target artifacts of a protected volume and are not redirected by the file-based write filter. The policy-based write filter can examine the write requests against any applicable policies to determine whether the write requests should be allowed to proceed. If the policy-based write filter determines that a write request is not allowed by policy, it can fail the write request to thereby prevent the targeted artifact from being updated in the protected volume.