DNS over HTTPS (DoH) offers enhanced privacy by encrypting DNS queries, making it harder for network observers to track your browsing activity. While this is beneficial for individual users, it presents challenges for network administrators, parents seeking to control children's internet access, and security professionals concerned about potential misuse. This guide explains how to block DoH on various platforms and networks.
There are several legitimate reasons why someone might want to block DoH:
Blocking DoH involves preventing clients from using DoH-capable resolvers. The approach varies based on the environment:
Many modern routers allow configuration of DNS settings. You can usually specify the DNS servers to use and sometimes even block specific ports used by DoH (typically port 443). Consult your router's documentation for specific instructions. This is often the most effective method for blocking DoH across all devices on the network.
Network firewalls can be configured to block outbound traffic on port 443 destined for known DoH resolvers (like Cloudflare's 1.1.1.1 or Google's 8.8.8.8). This requires identifying the IP addresses of these resolvers and configuring rules to block their connection over port 443. This is more complex than router configuration and requires advanced networking knowledge.
Warning: Incorrectly configuring firewall rules can disrupt legitimate traffic, so proceed with caution and test thoroughly.
Blocking DoH at the firewall is challenging due to the use of port 443 for HTTPS traffic. Carefully crafted rules are needed to avoid blocking legitimate HTTPS connections. Incorrectly configured rules can lead to significant network disruption.
If you manage your own DNS server, you can configure it to reject or block DoH requests. This involves setting up appropriate DNS policies to handle requests for DoH endpoints. This is a highly technical approach and requires significant DNS administration expertise.
Some applications allow configuring their DNS settings directly. You could try setting the DNS to an internal or controlled DNS server, but this is not foolproof as some applications may bypass these settings.
Using a proxy server can provide an intermediary that intercepts and controls DNS traffic. The proxy server can be configured to block DoH requests before they reach the client's machine. This approach is effective but adds another layer of complexity to the network configuration.
Completely blocking DoH might be difficult due to the use of port 443. Clients might try to use other ports or alternative DoH providers. Regular updates and monitoring are necessary to stay ahead of potential circumvention attempts. Furthermore, blocking DoH may impact the privacy of users relying on it for legitimate privacy concerns. A balanced approach that considers security and user privacy is crucial.
Blocking DNS over HTTPS involves technical complexities and requires careful consideration of the potential impact on network functionality and user experience. Choosing the right approach depends on your specific needs and technical capabilities. Always carefully test any changes made to your network configuration to avoid disrupting legitimate internet access.