Recursive DNS Server TTL Control for Cache Security
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Solution Overview
Problem
The existing DNS system is vulnerable to attacks due to its connectionless nature, leading to issues with hijacked or improper DNS records persisting in caches for extended periods, exposing users to malicious servers, as attackers can spoof source addresses and hijack DNS responses without error correction, making it difficult for organizations to systematically flush cache invalid records.
Innovation Solution
A method for setting a maximum Time-To-Live (TTL) value for DNS records at recursive DNS servers, allowing clients to control the processing of DNS records, and providing a cache flush mechanism to quickly remove invalid records, thereby reducing exposure to malicious servers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If DNS records are cached for extended periods to improve resolution efficiency, then DNS query speed is improved, but the system becomes vulnerable to hijacked or improper DNS records persisting in caches, exposing users to malicious servers
Solution Approach 1:
The patent implements preliminary validation of DNS records against security policies before caching them. The recursive resolver checks whether cached DNS records match authorized domain names and IP addresses according to pre-configured security policies, preventing malicious records from being cached in the first place
Solution Approach 2:
The system implements feedback mechanisms where DNS validation results are used to dynamically adjust caching behavior. When improper or hijacked records are detected, the system provides feedback to flush or invalidate affected cache entries, ensuring that security concerns trigger immediate corrective actions
2Ease of operation
If the DNS system uses connectionless communication to simplify operations, then ease of operation is improved, but the system becomes vulnerable to spoofed source addresses and hijacked responses without error correction
Solution Approach 1:
The patent introduces an intermediary security validation layer between the connectionless DNS communication and the caching system. This intermediary validates DNS responses against security policies, checks source address authenticity, and ensures that only authorized DNS records are cached, thereby protecting against hijacking while maintaining communication simplicity
Solution Approach 2:
The system applies preliminary anti-action by proactively validating DNS responses against known malicious patterns and unauthorized changes before they can cause harm. Security policies are pre-configured to identify and block spoofed responses, preventing hijacking attempts before they compromise the DNS cache
3Device complexity
If organizations use default DNS caching without customization to reduce complexity, then device complexity is reduced, but they cannot systematically flush cache invalid records when security issues arise
Solution Approach 1:
The patent implements dynamic DNS cache management where TTL values and cache validity are adjusted based on security conditions. When security issues are detected, the system dynamically flushes or invalidates affected cache entries, allowing organizations to maintain simple default operations while gaining the ability to respond to security incidents
Solution Approach 2:
The system provides universal DNS cache management that combines default caching operations with security-driven flushing capabilities in a single system. Organizations can use the system with default settings for simple operations, and the same system automatically provides cache flushing and validation capabilities when security issues arise, eliminating the need for separate complex configurations
Data Source
AI summary
Provided is a method for assigning a time-to-live (“TTL”) value for a domain name system (“DNS”) record at a recursive DNS server. The method comprises obtaining, from a client, the TTL value for the DNS record; and storing, in a memory of the recursive DNS server, the TLL value, an identifier of the client, and the DNS record.