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A transparent DNS proxy is the practice of intercepting DNS requests destined for a specific recursive DNS server (like DNSFilter) and sending the DNS requests to an entirely different DNS server.

When traffic is proxied users can see issues like connection failure error pages when visiting a website or a DNSFilter Site won't activate and shows offline status. 

Who is typically proxied?

Most "hardwired" ISPs (cable, DSL, fiber) in North America and Europe are not using transparent DNS proxies.

Satellite ISPs and Telecom providers (3g/4g/LTE) are commonly using transparent DNS proxies for performance reasons.

Proxying can happen via:

• Firewall (Direct NAT)
• Network Security Appliance (Security Feature)
• Software (Security Feature)
• ISP DNS Caching

Transparent proxying is typically employed for one of these reasons:

• Security (Local network) - To prevent the circumvention of a content filtering service (such as DNSFilter)
• Government Regulation - ISPs in Africa, Asia, and The Middle East typically have enforcement of government-mandated content filtering and/or traffic logging
• Satellite ISPs / Mobile ISPs - DNS requests are cached to increase performance