Agent skill

implementing-zero-trust-dns-with-nextdns

Implement NextDNS as a zero trust DNS filtering layer with encrypted resolution, threat intelligence blocking, privacy protection, and organizational policy enforcement across all endpoints.

View SKILL.md on GitHub Repository
Stars 4,300
Forks 470

Install this agent skill to your Project

npx add-skill https://github.com/mukul975/Anthropic-Cybersecurity-Skills/tree/main/skills/implementing-zero-trust-dns-with-nextdns

SKILL.md

Implementing Zero Trust DNS with NextDNS

Overview

NextDNS is a cloud-based DNS resolver that provides encrypted DNS resolution (DNS-over-HTTPS and DNS-over-TLS), real-time threat intelligence blocking, ad and tracker filtering, and granular DNS policy enforcement. In a zero trust architecture, DNS is a critical control point -- every network connection begins with a DNS query, making DNS filtering an effective layer for blocking malicious domains, preventing data exfiltration via DNS tunneling, enforcing acceptable use policies, and gaining visibility into all network communications. NextDNS processes queries using threat intelligence feeds containing millions of malicious domains updated in real-time, blocks cryptojacking and phishing domains, detects DNS rebinding attacks, and supports CNAME cloaking protection. For enterprise environments, Microsoft's Zero Trust DNS (ZTDNS) feature on Windows 11 extends this concept by enforcing that endpoints can only resolve domains through approved protected DNS servers.

When to Use

  • When deploying or configuring implementing zero trust dns with nextdns capabilities in your environment
  • When establishing security controls aligned to compliance requirements
  • When building or improving security architecture for this domain
  • When conducting security assessments that require this implementation

Prerequisites

  • NextDNS account (free tier: 300,000 queries/month; Pro: unlimited)
  • Network devices supporting DoH or DoT configuration
  • Administrative access to endpoint DNS settings
  • Understanding of DNS protocol and resolution chain
  • Familiarity with organizational acceptable use policies

Architecture

    Endpoint Device
         |
    DNS Query (Encrypted)
         |
    +----+----+
    |  DoH/DoT |  (DNS-over-HTTPS or DNS-over-TLS)
    |  Tunnel  |
    +----+----+
         |
    +----+----+
    | NextDNS  |
    | Resolver |
    +----+----+
         |
    +----+----+------+--------+
    |         |       |        |
  Threat   Ad/Tracker Privacy  Parental
  Intel    Blocklists Controls Controls
  Check    Check      Check    Check
    |         |       |        |
    +----+----+------+--------+
         |
    ALLOW or BLOCK
         |
    Response to Endpoint

Configuration Setup

NextDNS Profile Configuration

Dashboard: https://my.nextdns.io

Configuration ID: abc123 (unique per profile)

Endpoints:
  DNS-over-HTTPS: https://dns.nextdns.io/abc123
  DNS-over-TLS:   abc123.dns.nextdns.io
  DNS-over-QUIC:  quic://abc123.dns.nextdns.io
  IPv4:           45.90.28.x, 45.90.30.x (linked to config)
  IPv6:           2a07:a8c0::xx, 2a07:a8c1::xx

Security Settings

Security Tab Configuration:
  [x] Threat Intelligence Feeds - Block domains from curated threat feeds
  [x] AI-Driven Threat Detection - Machine learning-based detection
  [x] Google Safe Browsing - Cross-reference with Google's threat database
  [x] Cryptojacking Protection - Block crypto mining domains
  [x] DNS Rebinding Protection - Prevent DNS rebinding attacks
  [x] IDN Homograph Attacks - Block internationalized domain name attacks
  [x] Typosquatting Protection - Block common typosquatting domains
  [x] DGA Protection - Block domain generation algorithm domains
  [x] NRD (Newly Registered Domains) - Block domains < 30 days old
  [x] DDNS (Dynamic DNS) - Block dynamic DNS services
  [x] Parked Domains - Block parked/unused domains
  [x] CSAM - Block child sexual abuse material domains

Privacy Settings

Privacy Tab Configuration:
  Blocklists:
    [x] NextDNS Ads & Trackers Blocklist
    [x] OISD (Full)
    [x] EasyPrivacy
    [x] AdGuard DNS Filter

  Native Tracking Protection:
    [x] Block Windows telemetry
    [x] Block Apple telemetry
    [x] Block Samsung telemetry
    [x] Block Xiaomi telemetry
    [x] Block Huawei telemetry
    [x] Block Roku telemetry
    [x] Block Sonos telemetry

  [x] Block Disguised Third-Party Trackers (CNAME cloaking)
  [x] Allow Affiliate & Tracking Links (optional, for business)

Allowlist and Denylist

Allowlist (domains that bypass all blocking):
  - login.microsoftonline.com
  - graph.microsoft.com
  - *.company.com

Denylist (always blocked regardless of other settings):
  - known-malicious-domain.com
  - unauthorized-cloud-storage.com
  - personal-email-provider.com  (if policy requires)

Endpoint Deployment

Linux (systemd-resolved)

bash
# Configure DNS-over-TLS with systemd-resolved
sudo tee /etc/systemd/resolved.conf << 'EOF'
[Resolve]
DNS=45.90.28.x#abc123.dns.nextdns.io
DNS=45.90.30.x#abc123.dns.nextdns.io
DNS=2a07:a8c0::xx#abc123.dns.nextdns.io
DNS=2a07:a8c1::xx#abc123.dns.nextdns.io
DNSOverTLS=yes
Domains=~.
EOF

sudo systemctl restart systemd-resolved

# Verify
resolvectl status
resolvectl query example.com

Linux (NextDNS CLI)

bash
# Install NextDNS CLI
sh -c 'sh -e $(curl -sL https://nextdns.io/install)'

# Configure with your profile
sudo nextdns install \
  -config abc123 \
  -report-client-info \
  -auto-activate

# Verify
nextdns status
nextdns log

macOS

bash
# Install via Homebrew
brew install nextdns/tap/nextdns

# Configure
sudo nextdns install \
  -config abc123 \
  -report-client-info

# Or configure via System Settings > Network > DNS
# Add DNS-over-HTTPS: https://dns.nextdns.io/abc123

Windows

powershell
# Install NextDNS CLI for Windows
# Download from: https://nextdns.io/download/windows

# Or configure DoH natively (Windows 11)
# Settings > Network & Internet > Ethernet/Wi-Fi > DNS
# Preferred DNS: 45.90.28.x
# DNS over HTTPS: On (Manual template)
# DoH Template: https://dns.nextdns.io/abc123

# PowerShell: Configure DoH
Set-DnsClientDohServerAddress -ServerAddress "45.90.28.x" `
  -DohTemplate "https://dns.nextdns.io/abc123" `
  -AllowFallbackToUdp $false `
  -AutoUpgrade $true

Router-Level Configuration

# Most routers support custom DNS servers
# For DoH/DoT-capable routers (pfSense, OPNsense, OpenWrt):

# pfSense DNS Resolver (Unbound):
# Services > DNS Resolver > Custom Options:
server:
  forward-zone:
    name: "."
    forward-tls-upstream: yes
    forward-addr: 45.90.28.x@853#abc123.dns.nextdns.io
    forward-addr: 45.90.30.x@853#abc123.dns.nextdns.io

# OpenWrt (using https-dns-proxy):
opkg update && opkg install https-dns-proxy
uci set https-dns-proxy.default.resolver_url='https://dns.nextdns.io/abc123'
uci commit https-dns-proxy
/etc/init.d/https-dns-proxy restart

Mobile Devices

iOS:
  Install NextDNS app from App Store
  Or: Settings > General > VPN & Device Management
  Install NextDNS configuration profile

Android:
  Settings > Network > Private DNS
  DNS Provider: abc123.dns.nextdns.io

  Or: Install NextDNS app from Play Store

Microsoft Zero Trust DNS (Windows 11)

For enterprise Windows environments, Microsoft's ZTDNS enforces that endpoints can only communicate with domains resolved through approved DNS servers.

powershell
# Enable ZTDNS (Windows 11 23H2+)
# Requires Windows Defender Firewall in enforcing mode

# Configure Protected DNS Servers via Group Policy:
# Computer Configuration > Administrative Templates > Network > DNS Client
# > Configure DNS over HTTPS (DoH) name resolution
# > Protected DNS servers: https://dns.nextdns.io/abc123

# Windows Firewall blocks all traffic to domains not resolved
# through the protected DNS server

Monitoring and Analytics

Log Analysis

NextDNS Analytics Dashboard provides:
  - Total queries over time
  - Blocked queries by category
  - Top domains (allowed and blocked)
  - Top blocked reasons (threat, ad, tracker)
  - Device-level breakdown
  - Geographic query distribution

Log Settings:
  Retention: 1 hour / 6 hours / 1 day / 1 week / 1 month / 3 months / 1 year / 2 years
  Storage Location: US / EU / UK / Switzerland
  Logging: [ ] Enable / [ ] Disable

API Integration

bash
# NextDNS API for automated monitoring
# Get analytics data
curl -H "X-Api-Key: your-api-key" \
  "https://api.nextdns.io/profiles/abc123/analytics/domains?from=-24h"

# Get blocked domains
curl -H "X-Api-Key: your-api-key" \
  "https://api.nextdns.io/profiles/abc123/analytics/domains?from=-24h&status=blocked"

# Export logs for SIEM integration
curl -H "X-Api-Key: your-api-key" \
  "https://api.nextdns.io/profiles/abc123/logs?from=-1h" \
  | jq '.data[] | select(.status == "blocked")'

Zero Trust DNS Policy Framework

Policy Tiers

Tier 1 - Security (Mandatory for all):
  - Threat intelligence blocking
  - Cryptojacking protection
  - DNS rebinding protection
  - DGA detection
  - NRD blocking (< 30 days)

Tier 2 - Privacy (Recommended):
  - Tracker blocking
  - Native telemetry blocking
  - CNAME cloaking protection

Tier 3 - Compliance (Organization-specific):
  - Category-based blocking
  - Custom allowlists/denylists
  - Time-based access policies
  - Log retention per regulatory requirements

Security Best Practices

  1. Enforce encrypted DNS: Block plaintext DNS (port 53 UDP/TCP) at the firewall
  2. Use NextDNS CLI on endpoints: Ensures per-device identification and logging
  3. Enable NRD blocking: Newly registered domains are overwhelmingly malicious
  4. Block DNS-over-HTTPS bypass: Ensure browsers use system DNS, not built-in DoH
  5. Review blocklists quarterly: Remove false positives, add organizational blocks
  6. Enable CNAME cloaking protection: Prevents tracker evasion via CNAME records
  7. Set appropriate log retention: Balance privacy with forensic needs (90 days recommended)
  8. Monitor for DNS tunneling: Watch for unusual query patterns and high entropy domains
  9. Deploy at router level: Catches all devices including IoT and unmanaged endpoints
  10. Combine with endpoint DNS: Defense in depth with both router and per-device filtering

References

Recommended Agent Skills

Expand your agent's capabilities with these related and highly-rated skills.

mukul975/Anthropic-Cybersecurity-Skills

mapping-mitre-attack-techniques

Maps observed adversary behaviors, security alerts, and detection rules to MITRE ATT&CK techniques and sub-techniques to quantify detection coverage and guide control prioritization. Use when building an ATT&CK-based coverage heatmap, tagging SIEM alerts with technique IDs, aligning security controls to adversary playbooks, or reporting threat exposure to executives. Activates for requests involving ATT&CK Navigator, Sigma rules, MITRE D3FEND, or coverage gap analysis.

4,300 470
Explore
mukul975/Anthropic-Cybersecurity-Skills

hunting-for-spearphishing-indicators

Hunt for spearphishing campaign indicators across email logs, endpoint telemetry, and network data to detect targeted email attacks.

4,300 470
Explore
mukul975/Anthropic-Cybersecurity-Skills

analyzing-malicious-url-with-urlscan

URLScan.io is a free service for scanning and analyzing suspicious URLs. It captures screenshots, DOM content, HTTP transactions, JavaScript behavior, and network connections of web pages in an isolat

4,300 470
Explore
mukul975/Anthropic-Cybersecurity-Skills

implementing-zero-standing-privilege-with-cyberark

Deploy CyberArk Secure Cloud Access to eliminate standing privileges in hybrid and multi-cloud environments using just-in-time access with time, entitlement, and approval controls.

4,300 470
Explore
mukul975/Anthropic-Cybersecurity-Skills

implementing-pam-for-database-access

Deploy privileged access management for database systems including Oracle, SQL Server, PostgreSQL, and MySQL. Covers session proxy configuration, credential vaulting, query auditing, dynamic credentia

4,300 470
Explore
mukul975/Anthropic-Cybersecurity-Skills

detecting-t1003-credential-dumping-with-edr

Detect OS credential dumping techniques targeting LSASS memory, SAM database, NTDS.dit, and cached credentials using EDR telemetry, Sysmon process access monitoring, and Windows security event correlation.

4,300 470
Explore

Didn't find tool you were looking for?

Be as detailed as possible for better results