Modern ISPs and network intermediaries routinely log DNS queries, creating persistent trails of user activity. This metadata collection enables both surveillance and DNS hijacking (often for ad injection, as practiced by providers like Cox Communications). While solutions like DNS-over-HTTPS (DoH) encrypt queries, they still require external resolution.

The DNS root zone (containing TLD information for .com, .net, etc.) is publicly available through zone transfers (AXFR) from root servers. The ICANN-maintained root zone file updates multiple times daily and can be mirrored locally using these methods:

# Example AXFR request for root zone
dig @a.root-servers.net . axfr

For a complete offline-capable solution, you'll need:

1. Regular zone transfers from root/TLD servers
2. Local authoritative DNS software (BIND, PowerDNS, etc.)
3. Recursive resolution capability

Configure BIND as both authoritative and recursive resolver:

// named.conf options
options {
    directory "/var/named";
    allow-transfer { none; };
    allow-recursion { localhost; };
    recursion yes;
};

zone "." {
    type master;
    file "root.zone";
    allow-update { none; };
};

Use cron to periodically refresh the zone:

#!/bin/bash
dig @f.root-servers.net . axfr > /var/named/root.zone
rndc reload

The root zone contains ~1500 TLD records, but complete resolution still requires:

• ~50MB storage for full zone data
• Millisecond-level latency for local queries
• Daily updates to stay synchronized

For partial coverage without full root replication:

# Mass-resolve Alexa top 1M sites
for domain in $(cat top-1m.csv); do
    dig +noall +answer $domain >> local-cache.db
done

Self-hosted DNS introduces new attack surfaces:

• Requires strict AXFR access controls
• Needs DNSSEC validation
• Must maintain update integrity checks

Creating a complete local copy of the root DNS zone is technically possible but comes with significant operational challenges. The root zone contains approximately 1,500 TLDs (Top-Level Domains) with their NS records, but the real complexity comes from maintaining the entire DNS hierarchy locally.

While AXFR (Authoritative Transfer) exists for zone transfers, root servers typically don't allow unrestricted transfers due to:

# Example dig command for testing zone transfer
dig @a.root-servers.net . AXFR
;; communications error to 198.41.0.4#53: connection refused

The root servers implement strict rate limiting and access controls to prevent massive zone transfers.

Here are three viable technical solutions:

1. Recursive Caching with Prefetch

Using Unbound with aggressive prefetching:

# unbound.conf extract
server:
    prefetch: yes
    prefetch-key: yes
    cache-max-ttl: 86400
    cache-min-ttl: 3600
    aggressive-nsec: yes

2. Root Zone File Mirroring

ICANN provides the root zone file via FTP:

#!/bin/bash
wget ftp://ftp.internic.net/domain/root.zone -O /var/lib/unbound/root.zone
unbound-control load_zone . /var/lib/unbound/root.zone

3. Full Recursive Resolver with Local Cache

Knot Resolver configuration example:

-- Knot Resolver config
modules.load('prefill')
prefill.config({
    [''] = {url='https://www.internic.net/domain/root.zone'}
})

• Storage requirements (~50MB for root + frequent TLD updates)
• DNSSEC validation overhead
• Maintenance of up-to-date NS records
• IANA's root zone update cycle (multiple times daily)

For those primarily concerned with privacy rather than complete autonomy:

# dnscrypt-proxy configuration
listen_addresses = ['127.0.0.1:53']
server_names = ['cloudflare', 'quad9-dnscrypt-ip4-filter-pri']