Zero Trust DNS is Here: Elevating Enterprise Security on Windows 11
When attackers target an enterprise today, they rarely begin with a blunt smash-through-the-front-door intrusion. They begin quietly by resolving a domain. In most cases, modern malware, phishing kits, and human-operated ransomware operators rely on DNS as the entry point to discover infrastructure, beacon command-and-control, and exfiltrate data. Thus, it is becoming even more important to secure DNS to help protect against increasingly frequent, complex, and expensive cyberattacks. Enterprises have invested heavily in Protective DNS services with cutting-edge threat intelligence to identify and block malicious domains in real time but if an endpoint device can simply bypass them, the entire Zero Trust posture is weakened. Today, Microsoft is closing that gap. Introducing Zero Trust DNS (ZTDNS) We are excited to announce that Zero Trust DNS (ZTDNS) is now generally available on Windows 11 Enterprise and Windows 11 Education editions. ZTDNS is a new enterprise security feature in Windows that helps ensure DNS policy configured on the enterprise DNS server is enforced on the device. This is an important advancement for organizations working to enable that outbound connectivity on managed Windows devices aligns with enterprise authorization and policy. ZTDNS provides device-level enforcement of an enterprise’s DNS policy, in-box on Windows 11 helping ensure devices only communicate with destinations the organization intends. It doesn’t require installing and managing additional agents or maintaining a “best effort” block list on each endpoint device. With ZTDNS, the enterprise DNS resolver becomes the policy source of truth and Windows becomes the enforcement point. For more information, check out our documentation. This can be particularly useful for organizations in highly regulated industries, or where compliance with NIST standards is of paramount importance. Without ZTDNS, the system DNS client could be pointed to a network-provided malicious DNS server, which can resolve unapproved domains and return incorrect resolutions to redirect the system to attacker’s endpoint. If the malicious DNS server uses encrypted DNS, IT administrators won’t be able to analyze the DNS traffic to prevent or mitigate potential attacks. Applications can use their own DNS client to completely bypass system policies. Also, system remains vulnerable to in-network attackers. ZTDNS protects against these attack vectors by mandating the use of Windows DNS client and only sending encrypted DNS queries to the trusted DNS servers. Since ZTDNS blocks all outbound connections and local name resolution by default, the system is protected against in-network threats. Why is ZTDNS needed? In enterprise scenarios, DNS is no longer just a lookup mechanism but a policy decision point. However, without device-level enforcement, attackers can hijack device DNS to: Redirect DNS queries from the device to a malicious or compromised DNS server Use their own encrypted DNS client and bypass system DNS client Bypass DNS completely with direct IP connections In such cases, organizations lose the ability to control which network destinations the endpoint is allowed to reach even if a Protective DNS service is used. ZTDNS addresses this by only allowing outbound connections to IP addresses that were resolved by the trusted DNS server for a query issued by the Windows DNS client. More importantly, it achieves this without terminating end-to-end encryption. How does ZTDNS work? ZTDNS integrates the Windows DNS client with the Windows Filtering Platform to help enforce domain-name-based network lockdown using encrypted DNS. ZTDNS is off by default and can be configured on a Windows 11 device with an enterprise-approved DNS over HTTPS (DoH) or DNS over TLS (DoT) server. When enabled, ZTDNS blocks all outbound IP-based connections by default and only allows outbound connections to IP addresses resolved by the trusted DNS server or those added to the manual exception list by the IT administrator. It mandates the use of encrypted DNS (DoH or DoT) and only trusts the DNS resolutions initiated by the Windows DNS client and answered by the trusted DNS server to create outbound allow exceptions. This helps provide a strong, enforceable control that aligns with Zero Trust principles: all destinations are untrusted by default unless specifically permitted. In a nutshell, when configured and enabled, ZTDNS will have the following effects on your Windows 11 device: Encrypted DNS enforcement (DoH or DoT) Default deny for outbound IPv4 and IPv6 traffic Dynamic allow listing of IP addresses returned by trusted DNS servers Static allow listing of IP addresses approved by the IT administrator via manual exceptions Centralized logging of permitted and blocked connections Deploying ZTDNS ZTDNS is available in the latest builds of Windows 11 Enterprise and Windows 11 Education. To deploy ZTDNS, enterprises can configure and enable it via: netsh commands JSON configuration We are also actively developing a Microsoft Intune experience for ZTDNS and we will share more information when the details are available. For detailed deployment guidance, check out our official documentation. Join Me at Microsoft Ignite 2025 For customers attending Microsoft Ignite 2025, please join us at session BRK258: Inside Windows Security, from client to cloud to learn more about ZTDNS. Alternatively, you can also visit the Windows Resiliency Initiative & Windows Security booth to discuss ZTDNS in depth. Securing the Present, Innovating for the Future Security is a shared responsibility. Through collaboration across hardware and software ecosystems, we can build more resilient systems secure by design and by default, from Windows to the cloud, enabling trust at every layer of the digital experience. The updated Windows Security book is available to help you understand how to stay secure with Windows. Learn more about Windows 11 and Copilot+ PCs. To learn more about Microsoft Security solutions, visit our website. Bookmark the Security blog to keep up with our expert coverage on security matters. Also, follow us on LinkedIn (Microsoft Security) and X (@MSFTSecurity) for the latest news and updates on cybersecurity.Announcing Public Preview of Zero Trust DNS
In today's evolving cybersecurity landscape, traditional perimeter defenses are no longer sufficient . As organizations embrace the Zero Trust security model, ensuring that devices only communicate with trusted network destinations becomes paramount. We are excited to announce the public preview of Zero Trust DNS (ZTDNS), a new feature in Windows 11 Insider builds designed to enforce domain-name-based network access controls, enhancing your organization's security posture. ZTDNS empowers enterprise IT administrators to natively apply outbound domain-name-based network access controls on Windows 11 endpoints. This helps prevent access to untrusted destinations, reducing the risk of a slew of network attacks from malware communication to data exfiltration. What is Zero Trust DNS? ZTDNS integrates the Windows DNS client with trusted Protective DNS (PDNS) servers to control outbound IP traffic based on domain names. When ZTDNS is configured on a Windows 11 device to use PDNS servers that support DNS over HTTPS (DoH) or DNS over TLS (DoT), ZTDNS ensures that: The Windows DNS client forces the use of encrypted DNS and queries are only sent to the configured PDNS servers. Outbound traffic is permitted only to IP addresses resolved by these trusted PDNS servers or to IP ranges with a manual exception plumbed by the IT administrator. All other IPv4 and IPv6 outbound traffic is blocked by default, adhering to the "deny by default" principle of Zero Trust. A log of attempted outbound connections is maintained on the device. This approach reduces the need for deep packet inspection or reliance on insecure signals like plain-text DNS or Server Name Indication (SNI) when attempting to determine the domain name associated with outbound traffic. This makes ZTDNS an important tool in the Zero Trust toolbelt since DNS traffic and SNI are increasingly being encrypted. It also aligns with Zero Trust principles by assuming all destinations are untrusted by default, only allowing connections to destinations explicitly permitted through DNS resolutions provided by trusted PDNS servers. For more information, visit our previous blog post on design of ZTDNS. Threats Zero Trust DNS Helps Mitigate Implementing ZTDNS can bolster your defenses against various network-based threats, including: DNS Hijacking: By ensuring that only DNS resolutions from trusted PDNS servers are used, ZTDNS helps prevent attackers from redirecting traffic to malicious sites. Malicious Communications: Blocking outbound connections to IP addresses not resolved through trusted DNS queries helps disrupt phishing and even non-administrative malware stagers and beacons. Data Exfiltration: Restricting outbound traffic to approved domains reduces the risk of sensitive data being transmitted to unauthorized destinations without conducting analysis of domain name resolution patterns. Getting Started with Zero Trust DNS NOTE: Public Preview of ZTDNS has officially ended. The instructions below are no longer supported. We appreciate you taking the time to test out ZTDNS in Public Preview. Your valuable feedback has helped us improve ZTDNS. For further assistance, please reach out to ztdnspreview@microsoft.com. To enable ZTDNS in your environment: Get a supported Windows 11 build Enroll your device in the Windows Insider Program (Canary channel) and update to build 27766+. Unlock ZTDNS In an administrator command prompt, run: reg add "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Dnscache\Parameters" /v Experiment4712 /d 0xbe8261eb /t REG_DWORD Reboot the device. Ensure all applications and services are configured to use the Windows DNS client Configure applications like Edge and Chrome to use the Windows DNS client instead of their custom client (disable BuiltInDnsClientEnabled policy). Add manual allow exceptions Teleconferencing applications like Teams use WebRTC which negotiates IP addresses for peers within a TLS tunnel and has no DNS visibility. These IP subnets are also publicly documented and need manual allow exceptions for the application to work with ZTDNS. Add manual allow exceptions for IP addresses that are necessary for your productivity applications/services but are not discovered through DNS. Here is a sample command, for manual allow exception, which needs to run in administrator command prompt: netsh ztdns add exception name=AppName description="Description of AppName" subnets=192.0.2.128/25,198.51.100.0/24,3fff::/48, 3fff:123::/38 Here is a link Microsoft 365 services that may need manual allow exceptions. Set your trusted Protective DNS server (needs to be DoH/ DoT capable) In an administrator command prompt, replace example data in following sample commands with information about your desired DNS server before running: netsh ztdns add server type=doh address=203.0.113.0 template=https://doh.resolver.example/dns-query netsh ztdns add server type=dot address=2001:db8::1 hostname=dot.resolver.example Enable ZTDNS ZTDNS can be enabled using Audit mode or Enforcement mode. Audit mode logs all expected ZTDNS behavior without the actual enforcement. Check out the next blog post for finding and comprehending ZTDNS logs. Enabling ZTDNS in audit mode is recommended before moving on to Enforcement mode. In an administrator command prompt, run: netsh ztdns set state enable=yes audit=yes Enforcement mode blocks untrusted traffic. In an administrator command prompt, run: netsh ztdns set state enable=yes audit=no Now you should have ZTDNS running! In a rare situation where you experience unexpected connectivity issues for some application, please restart the application. If the issue persists, please reboot the device. Disable ZTDNS ZTDNS is a powerful lockdown feature. In case you lose network connectivity due to misconfiguration, you can disable ZTDNS to restore your network connectivity. In an administrator command prompt, run: netsh ztdns set state enable=no audit=no Note: ZTDNS is currently in Public Preview and is intended for evaluation and feedback only. Do not deploy in production environments. Breaking changes may occur before General Availability (GA). Check out the next blog post Troubleshooting Zero Trust DNS for information on ZTDNS logs, sharing feedback and bug reports with the team. Join Me at RSAC 2025 I am excited to share that I will be attending the RSA Conference 2025! If you are planning to be there, stop by Microsoft booth N-5744 or Microsoft Security Hub and ask for Aditi Patange to discuss how ZTDNS can enhance your organization's security posture. Securing the Present, Innovating for the Future Security is a shared responsibility. Through collaboration across hardware and software ecosystems, we can build more resilient systems secure by design and by default, from Windows to the cloud, enabling trust at every layer of the digital experience. The updated Windows Security book is available to help you understand how to stay secure with Windows. Learn more about Windows 11 and Copilot+ PCs. To learn more about Microsoft Security solutions, visit our website. Bookmark the Security blog to keep up with our expert coverage on security matters. Also, follow us on LinkedIn (Microsoft Security) and X (@MSFTSecurity) for the latest news and updates on cybersecurity.
Issue with DnsConnectorDelivery
Background: We are currently migrating from Exchange 2016 to 2019 in a hybrid environment. We have 2 2016 servers both in our main datacenter, and 2 2019 servers, one in our main datacenter and one in our offsite datacenter. Backup datacenter has its own DCs that are replicas of our main datacenter's DCs. Exchange 2019 has been installed and updated to CU 11. Problem: When I run the hybrid configuration wizard and select all 4 servers to be included in the send and receive connectors, everything completes and no errors appear. However, mail gets stuck in the DnsConnectorDelivery queue on the server in our backup datacenter. The NextHopDomain for the stuck mail is our M365 domain, domain.mail.onmicrosoft.com As soon as I remove the server in the backup site from the send and receive connectors, mail flows correctly again. I've done a lot of internet searching and it seems the issue has something to do with our MX record, but both domains have the correct record in their DNS. What could be causing the issue? Any help is appreciated!
Windows Server 2019 AD & DNS replication
Hello, I'm running into issues with AD & DNS replication on a recently joined server in our environment. Environment: Three writable DCs in separate sites: Server A (Site A) – Windows Server 2019, AD DS & DNS (healthy) Server B (Site B) – Windows Server 2019, AD DS & DNS (healthy) Server C (Site B, new) – Windows Server 2019, AD DS & DNS (failing) Issues Observed Inbound replication to Server C from Server A & Server B successfully propagates for both AD and DNS zone/record changes. Outbound replication from Server C to Server A & Server B fails for both AD and DNS zone/record changes. Server A logs Event ID 1311 (KCC). Server A & B logs Event ID 1925 when trying to establish the link to Server C. What I’ve Tried: Pointed each servers NIC's to a heathy DC with the correct suffix. I've checked any windows FW and network FW rules to make sure no blockages. Verified A+SRV records for both heathy DC's. Confirmed AD-Integrated zones on all 3 servers show correct ACLs and records. I've tried running repadmin → still errors. Tested RPC connectivity: TCP 135 open. Ensured subnets/site mappings are correct in Sites and Services. I've tried to seed a zone and record on the healthy servers in efforts of t/s. Any help would be greatly appreciated!DNS lookup performance
Hello all I've got this to do what I want but thought I'd run it past people who know more than me in the hope someone would be kind enough to advise on the following. The intention is to run this every few minutes using task scheduler, I'll push to one or more machines with an RMM. Questions. Is this an efficient an accurate way to do this? Are there any improvements anyone wants to suggest for the code Am I re-inventing a wheel that I can get somewhere for free or low cost? I'm waiting for the new version of GRC's DNS testing tool so this is a stopgap unless it works well enough. TIA # Define an array to store the DNS Servers to be queried with thier FQDN and IP address $dnsServers = @() # Add 5 hosts with their FQDN and IP addresses $dnsServers += [PSCustomObject]@{ FQDN = "OurDNS1"; IPAddress = "14.15.16.17" } $dnsServers += [PSCustomObject]@{ FQDN = "OurDNS2"; IPAddress = "11.12.13.14" } $dnsServers += [PSCustomObject]@{ FQDN = "Cloudflare"; IPAddress = "1.1.1.1" } $dnsServers += [PSCustomObject]@{ FQDN = "Quad9"; IPAddress = "9.9.9.9" } $dnsServers += [PSCustomObject]@{ FQDN = "Google"; IPAddress = "8.8.8.4" } # Define an array to store target FQDNs $targetFqdns = @( "bbc.co.uk", "www.porsche.com", "www.amazon.co.uk" ) # Get the current date in yyyy-MM-dd format $currentDate = Get-Date -Format "yyyy-MM-dd" # Define the path to the CSV file with the current date in the filename $filePath = "$PSScriptRoot\DNSResults_$currentDate.csv" # Initialize the CSV file with headers if it doesn't exist if (-not (Test-Path $filePath)) { "Timestamp,Milliseconds,TargetURL,DNSServerIP,DNSServer" | Out-File -FilePath $filePath } # Loop through each target host and then each DNS server foreach ($targetFqdn in $targetFqdns) { foreach ($dnsServer in $dnsServers) { # Measure the time taken to run the command $measure = Measure-Command -Expression { nslookup $targetFqdn $dnsServer > $null 2>&1 } # Get the current date and time in ISO 8601 format $timestamp = Get-Date -Format "yyyy-MM-ddTHH:mm:ss" # Get the total milliseconds and round up to a whole number $milliseconds = [math]::Ceiling($measure.TotalMilliseconds) # Append the timestamp, milliseconds, domain, server, and name to the CSV file $result = "$timestamp,$milliseconds,$targetFqdn," $dnsServerUSed = "$($dnsServer.IPAddress),$($dnsServer.FQDN)" $output = $result + $dnsServerUsed $output | Out-File -FilePath $filePath -Append } }
DNS proxy for splunk cloud net rule still denied
I have set up my azure FW for DNS proxy and changed the v-nets dns to the private IP of the FW. I have the firewall pointing to custom dns servers. I created a FW rule to allow port 9997 to our splunk cloud instance from any IP. clients are still denied On a VM I can verify its using the FW IP, and I see dns queries in the logs. I'm not sure what I'm missing.
