Overview

Category-based filtering is a mechanism for managing internet access through content filtering by organizing websites into groups and applying specific rules to them. Operating at the DNS level, this approach serves three primary functions: security, workplace productivity, and child safety.

How It Works

The system follows a straightforward process:

• Websites (domains) are organized into content-based categories
• A DNS filtering service examines each website request on a network
• Access is either permitted or blocked according to established rules

Content Filtering Categories

Domains receive classification through advanced evaluation systems that consider site content and context, proprietary filtering provider data, third-party intelligence sources, and community feedback. For example, Netflix typically falls under "Streaming Video," while LinkedIn might be categorized as both "Business and Economy" and "Social Networking."

DNS Filtering Process

The filtering sequence operates as follows:

• User enters a domain or clicks a link
• DNS filter intercepts the request before it reaches its destination
• System checks domain against its database
• Filter either grants access by resolving to IP address or blocks by refusing resolution

DNS filtering works at the network level and remains independent of operating system or application type.

Common Category Types

• High Risk: Malware, Phishing, Botnets -- used for security measures.
• Workplace Policy: Social Media, Gaming, Streaming -- used for managing productivity.
• Compliance: Adult Content, Gambling, Weapons -- used for meeting legal standards.
• Custom: Custom URLs/IPs -- used for tailored organizational needs.

CleanBrowsing offers 23+ predefined categories to cover a wide range of filtering needs.

Key Advantages

Security Protection: Blocks high-risk websites associated with malware, phishing, and social engineering threats.

Workplace Focus: Research indicates 58% of employees spend over four hours weekly on non-work sites, prompting 89% of companies to implement restrictions.

Flexible Control: Modern solutions enable custom policies for different user groups, schedule-based access, remote deployment, and real-time updates.

Implementation Considerations

When selecting a filtering solution, evaluate:

• Number and flexibility of predefined categories
• Real-time monitoring and reporting capabilities
• Customer support quality
• Deployment options (cloud or on-premises)
• Scalability and cost structure

Common Challenges

Filtering Accuracy: Systems may block legitimate content or miss harmful material through over-blocking or under-blocking errors.

HTTPS Encryption: Most websites now use HTTPS, complicating content inspection. Two management approaches include certificate substitution and SNI (Server Name Indication) analysis.

Content Management: The constantly evolving web requires real-time analysis, machine learning classification, and frequent policy updates.

Effectiveness at Scale

CleanBrowsing processes over 355 billion requests monthly across 70 data centers, demonstrating the reliability and scale of modern filtering systems.

Summary

Category-based filtering provides security by blocking harmful websites and suspicious domains, productivity by limiting unnecessary sites and optimizing bandwidth, compliance by supporting regulatory requirements like CIPA for schools, and customization by enabling tailored rules for different user groups.