DNS outage (DNS downtime) – what does it mean? 

The DNS outage (a.k.a. DNS downtime or DNS failure) is a period of time when the domain name can’t be resolved to its IP address. The clients will send a DNS query for a domain name, but the DNS recursive will either answer with the old IP address from its cache, which will not respond, or it will try to query the DNS authoritative name server of the domain name won’t get an answer. 

What causes DNS outages? 

DDoS attacks

DDoS or a denial of service attack, is a type of cyber-attack that involves multiple devices that work together, targeting a victim’s computer, with a large amount of traffic intending to make it unable to answer any more queries. To prevent any problems that a DDoS attack can cause, you will need a load balancing that can share the traffic between your servers, even if it is very strong. And also, you will need DDoS-protected servers. 

Maintainance of the authoritative name server

If you are using only one authoritative name server, whatever happens to it, can affect your DNS. If it needs updates and reboot, the time that it takes, the server won’t be able to respond to DNS queries. Updates and maintenance are needed, so you better have a Secondary DNS that can answer the queries meanwhile. 

A problem in the data center, where the authoritative name server is

The cloud equipment does not magically hover over the Earth. Instead, it resides in multiple data centers. These places can have problems like long-lasting electricity outages, natural disasters affecting the area, fire, or other problems. If you are using a cloud service, these issues are out of your hands, but you can use multiple servers in multiple data centers. If one is down, still, there will be more to answer the queries. 

Bad configuration

Errors in DNS configuration can cause DNS downtime. It can be a human mistake, like badly addressing caused by misspelling the IP address or domain name, script error, wrong firewall configuration, etc. 

If it is a misspelled problem, you can try to query the domain name and the IP address to see which does respond and which does not. 

If it is the firewall, you can check the ports if they were allowed. 

DNS propagation delay

When you add or remove DNS records (like A or AAAA records), the changes are not always instant. You are editing the zone file inside the Primary DNS server, and you can propagate to your Secondary DNS servers, but there are many DNS recursive servers that you don’t control. They can keep your old IP address and provide it to clients, even after you published a new one. 

What you can do about the DNS propagation is to push the zone transfer to your Secondary servers and to keep lower TTL values for your DNS records. 

It is not technically a DNS outage because it will affect only those with the older cached IP address of the domain name, but it was worth mentioning it.

How to avoid DNS downtime (outage)

The best way to avoid DNS outages is to have a robust DNS network that provides redundancy and can withstand strong traffic. The more servers you have, the better you are going to be prepared. Additional features might also facilitate the DNS administration and automate the process of handling problems. 

Use Secondary DNS services

A secondary DNS service provides you with the opportunity to use multiple Secondary DNS servers, which can be set as Secondary authoritative nameservers. They will have a copy of the zone file with the DNS records. They can answer queries for your domain, just like the Primary one. The big advantage is that they will keep answering even if the Primary is experience downtime. Having Secondary DNS is your DNS backup solution. 

You can learn more about it in this article, “What is backup DNS?”, and you can try our Secondary DNS plans with a 30-day free trial. 

Use DNS load balancing

DNS load balancing is also another nifty way to lower the chance of DNS outages. It is a mechanism for administrating the DNS traffic between the DNS server, based on criteria like the number of active connections, specific algorithm, time of connection, etc. 

It will reduce the stress on a particular DNS server and spread it between the network. 

It can help in case of a DDoS attack but also in a natural spike in traffic caused by increased clients’ queries. It can help you during a promotional period when you are experiencing higher traffic.

Be prepared with DNS Failover

DNS Failover is a trigger that will activate in case of a nameserver’s failure. It can automatically redirect the traffic without any human interaction, based on the information it gets from DNS monitors like ICMP ping, UDP requests, HTTP checks, etc. It is an easy way to keep your clients’ happy and provide DNS resolution, even if some of your DNS servers are experiencing some problems. We offer DNS Failover service with all of our paid plans.

Also, we recommend you to check our Brand new Monitoring service!

How to diagnose DNS outages?

When facing a DNS outage, quick diagnosis is essential to restore functionality. Follow these steps to pinpoint the problem:

• Ping the Domain

Use ping to check if the domain resolves and the server responds.

ping example.com

If it doesn’t resolve, it’s likely a DNS issue.

• Test DNS Resolution with nslookup

Verify if DNS is working by querying your DNS server with nslookup.

nslookup example.com

If it returns an IP address, DNS is working for that domain. But if it fails, the DNS server may be down or misconfigured.

• Run dig for detailed queries

Use dig for detailed DNS resolution data, including specific DNS record types.

dig example.com

Add +trace to follow the query path through name servers and find where it fails.

• Test with Alternate DNS Servers

Query public DNS servers (like Google’s 8.8.8.8) to rule out provider-specific issues.

nslookup example.com 8.8.8.8

If the domain resolves with a different DNS server, it suggests the problem is with your original DNS provider.

• Check DNS Propagation Delays

If you’ve recently made DNS changes (such as updating A or MX records), delays in DNS propagation could be the culprit. Use online tools like ClouDNS Free DNS tool to check whether your DNS records have propagated across global DNS servers.

• Check for DDoS attacks or high traffic loads

DNS outages can be caused by Distributed Denial of Service (DDoS) attacks or heavy traffic loads. Tools like TCPdump can help capture and analyze DNS traffic to detect abnormal patterns, such as a flood of queries or unusual IP activity.

Example:

sudo tcpdump -i eth0 port 53

This command captures DNS traffic, allowing you to inspect for signs of an attack. For real-time detection, combine TCPdump with network monitoring tools and DDoS mitigation services.

Troubleshooting 

What can you do when your domain is not reachable? 

As DNS administrator of the domain name, you can: 

• Suppose you have recently finished a DNS delegation. You might need to way up to 24 hours, so the changes are well propagated. 
• Check if you have paid for your domain name. If you have forgotten to pay your domain name, it won’t answer queries anymore when it expires. Set reminders for domain renovation and don’t miss the time. 
• Use the ping command to ping the DNS server from different locations to see if it is responding to any DNS requests. It is possible that you haven’t set up your nameservers correctly, and they are working but not answering queries for the domain name. 
• Try to reach the DNS server by using its IP address. If you can reach it, there might be a badly configured A or AAAA record that does not link well the domain name and its IP address. 
• Check your DNS monitor and see how the traffic is going. If you can’t see the monitor’s log, check if there were any unusual activities before the server stopped working. For example, it could have been a DDoS attack. If it is still happening, you can redirect the traffic and stop it. 

As a client who can’t reach a site: 

• You can have problems with the DNS cache of your device. You can flush the DNS of your device and your browser. This action will remove the previous DNS records that you have, and your device will search again for the A or AAAA record of the site you want to visit. If you had an older IP address, this could fix it. 
• Maybe your router is the problem. The router has a recursive DNS server that may need to be restarted. Pull its plug, then wait around a minute and connect it again. It should reboot and start working well again. 

Monitor your DNS server

Monitor your DNS for any strange pattern in traffic. There are different automatic monitors that you can set to see the traffic behavior. If something strange happens, you can see in almost real-time any changes and use the information to take action. 

You can monitor the DNS from different locations. That way, you can see if the problem is very local, is it regional, continental, or global. It will be easy to spot the problem.
DNS monitoring works best in combination with DNS Failover. You can set the monitor with the parameters that you prefer, and it will notify you and show you the data. But when you also have DNS Failover, you can connect this data and trigger automatic even in case of a down server. It can deactivate DNS records and replace them with working. It can also react in case the server gets up and add it to the list again. 

ClouDNS offers DNS Failover service for all of its paid customers. You can set it up and activate it for your domain fast and easily.

What are the consequences of a DNS outage?

If a DNS outage occurs, it could have a negative impact on your entire organization and community of customers. When DNS (Domain Name System) is down, websites, applications, and online services related to the domain name, such as emails, won’t function correctly. Unfortunately, that has the potential to damage operations, revenue, and brand reputation. In addition, you should act fast and quickly get it up and running again to regain all the temporarily lost functionality.

Yet, let’s assume the functionality of the DNS operations was seriously interrupted for a prolonged period of time. In that case, a DNS outage can potentially cause devastating consequences to the companies with an online presence. Here are some of the most common effects during this time: 

• Miss potential visitors
• Lose potential sales
• Have issues with services like email, FTP, VoIP, etc.
• Productivity losses
• Damage to reputation
• Impact on customers and strategic partners
• Diminished competitive advantage

It is crucial to implement all precautionary measures to avoid DNS outage’s negative influence on your business.

The biggest DNS outages in the history

• 2016 Dyn DNS Interruption: A significant disturbance shook the internet when Dyn, a leading DNS service provider, fell victim to an attack. Websites with heavy traffic, such as Twitter, Spotify, and Reddit, experienced outages. This event underscored the vulnerabilities tied to unsecured IoT devices.
• 2019 Cloudflare Outage: A misconfigured web application firewall rule caused a major disruption in Cloudflare’s services, impacting millions of websites.
• 2019 Google Cloud Outage: In June 2019, Google Cloud Platform experienced a significant outage that affected multiple services, including Gmail, YouTube, and Google Cloud Storage. A configuration change intended for a small number of servers in a single region was mistakenly applied to a larger number of servers across several neighboring regions.
• 2020 AWS Outage: In November 2020, Amazon Web Services (AWS) faced a significant outage that affected several services reliant on AWS’s infrastructure. This incident disrupted many online services and platforms, highlighting the vulnerabilities in centralized cloud infrastructures.
• 2021 Fastly Global Outage: In June 2021, a major global internet outage occurred, affecting numerous high-traffic websites including Reddit, Twitch, and even the UK government’s official website. This was traced back to a software bug in the Fastly CDN network, a critical infrastructure provider for many internet services.
• 2022 Microsoft Azure DNS Outage: In mid-2022, Microsoft’s cloud service, Azure, experienced a DNS outage. It impacted a wide range of services, from basic operations in Azure to third-party applications relying on Azure’s infrastructure. The outage underscored the need for robust failover systems and redundancy in cloud services.

Conclusion

A huge DDoS attack can lead to a DNS outage even if you have excellent infrastructure. But applying all the measurements can lower the time and the frequency of the DNS outages. Be prepared and intelligently manage your DNS traffic to be able to provide excellent service for your clients. Keep your business up!

The post What is a DNS outage (DNS downtime), and how to avoid it? appeared first on ClouDNS Blog.

DNS Monitoring explained

DNS Monitoring gives you the ability to manage and examine the performance of a DNS server. The main goal is to assist you with detecting server-side and client-side DNS issues. In addition, it guarantees the health of DNS servers by sending a DNS request. You are able to choose different query types depending on the DNS record you want to check, for example, A, AAAA, MX, NS, PTR, or CNAME. Then you specify a required expected response that is compared to the actually received response.

DNS Monitoring has a very important role in your network Monitoring service. Moreover, it ensures the safety and proper connection between the end-users and the website or service that they want to use. It is extremely useful when it comes to the fast detection of unpleasant issues or for recognizing potential security breaches. Additionally, it is helpful for stopping some popular malicious attacks. Thanks to the regular checks, you can effortlessly detect unexpected issues or localize DNS outages. As a result, you can prevent a large negative impact on your website or on the safety of your users that want to reach your services by detecting and resolving the problem fast.

Why is DNS Monitoring important?

The Domain Name System (DNS) is an essential part of the Internet. Yet, it was not designed with security in mind. For that reason, cybercriminals have developed ways to take advantage of its vulnerabilities. Therefore, DNS monitoring is vital for helping you protect your online presence and catch issues before they become significant problems. DNS monitoring gives you the ability to recognize several different DNS errors. The majority of them result from malicious attempts and could be a significant threat to your security. On the other hand, there are also communication flow interruptions. They compromise the functionality of your domain’s DNS resolution process and lower the traffic toward your site.

Configuration Errors

DNS Monitoring can detect errors like incorrect IP addresses and assure that outages are not prolonged. The less time your website or service is down, the less your traffic flow is interrupted. That way, you can maintain and increase your uptime, and every user that wants to reach your website (or service) will have that opportunity without any difficulties.

A configuration error can stop users from reaching your website and make it seem like their internet is not acting correctly. This could drive traffic away from your domain and meddle with your business.

DNS Spoofing (DNS poisoning)

DNS Spoofing, also commonly known as DNS poisoning, is a popular cyber threat that cybercriminals use. Recursive DNS servers hold the hostname data with all related DNS records for a particular amount of time (depending on the TTL). That way, they operate more efficiently because they do not repeat the resolution process for the same IP address. However, it also leads to vulnerabilities.

Cybercriminals insert fraudulent data into the DNS cache on the server, like fake IP addresses. Commonly, that is achieved due to viruses and malware. As a result, the users’ requests are directed to a malicious phishing website, which looks similar to the original one. There they type their sensitive information, such as passwords, credit card details, etc. A lot of people do not even notice that they have been directed to malicious pages. No one wants to put its clients at risk of phishing schemes. Additionally, compromising user information can seriously impact your business.

DDoS and DoS Attacks

Distributed Denial of Service (DDoS) and Denial of Service (DoS) attacks are massive cyber threats that are able to bring down your server. They involve large amounts of fake traffic with the main goal of overcoming your resources and making your website or service unavailable for regular users. It is important to mention that the earlier the attack is detected, the more quickly it can be handled. Therefore, it is best to stop it before the DNS records on the server become weaponized by the cybercriminals.

DNS Tunneling

DNS Tunneling is another cyber threat that attackers commonly use. Typically, DNS servers handle a massive amount of traffic, and there are no security measures regarding the exchanged data packets. DNS Monitoring can help detect tunneling and serve to prevent any further data from being exchanged. This is an essential addition to your existing security measures.

DNS outage

DNS outage does not allow your users to connect and reach your website or service. It is possible to last just several minutes, but it could continue up to several hours or even days. So you can probably imagine how seriously it can affect your business and services. With DNS Monitoring, you can easily find and understand where the issue is coming from and quickly fix it.

How does it work?

You can find DNS monitoring as a part of ClouDNS Monitoring service. It works by regularly checking if the DNS server responds to all DNS queries. With such type of check, you can initiate DNS queries for a desired hostname and query type – A (for IPv4), AAAA (for IPv6), MX, NS, PTR, or CNAME. There are two scenarios that follow once you set your expected response.

• The check is marked UP, when the received response is equal to the required expected one.
• The check is marked DOWN, when the received response is not equal to the required expected one.

The DNS monitoring check validates the conditions of DNS servers by sending a DNS request and comparing the received response with the expected one.

You can also take a look at our article about DNS monitoring Checks!

Why do you need it?

DNS monitoring is necessary because DNS performance is essential to your network, servers, and applications. Thanks to the DNS servers, your website or service works effectively and efficiently, yet they should be monitored for vulnerabilities. In case you neglect their adequate supervision, you may compromise both the security of your business and your clients.

With the ClouDNS Monitoring service, you can keep an eye on your servers and quickly detect any issues. As you know, timing is crucial, so the fast resolving of the issues is going to guarantee the integrity of your servers. So, as a result, everything should continue operating smoothly.

Benefits of DNS monitoring

DNS monitoring is a critical component of any organization’s network management strategy. By monitoring DNS traffic, organizations can proactively identify and address issues before they escalate. Here are some of the main benefits of the implementation of DNS monitoring:

• Improved Server Availability

It can help improve server availability by identifying and resolving issues that can cause downtime or service disruptions. For example, DNS servers can be vulnerable to hardware or software failures, network connectivity issues, and cyber attacks, which can affect the availability of websites and other online services. DNS monitoring services can detect and alert tech teams of problems before they escalate, allowing them to take proactive measures to resolve them.

• Improved DNS Server Troubleshooting

DNS monitoring can help improve DNS server troubleshooting by providing visibility into the DNS infrastructure and the flow of DNS queries. Tech teams can use DNS monitoring tools to identify blockages, misconfigurations, and other issues affecting the performance of the DNS server. The information helps them troubleshoot and resolve issues more quickly, minimizing downtime and service disruptions.

• Faster Detection of Outages

DNS monitoring can be useful for detecting outages faster by providing real-time visibility into the DNS infrastructure. It can alert tech teams about issues, such as DNS server failures or network connectivity problems, as soon as they occur. That way, IT teams can quickly identify the root cause of the problem and take action to restore services.

Monitoring Plan

Comparison with other monitoring techniques

DNS monitoring is a specialized approach focusing on the health and security of the Domain Name System, which is crucial for translating domain names into IP addresses. While DNS monitoring is vital, it’s one part of a broader network monitoring strategy that includes other techniques such as network performance monitoring, application monitoring, and security information and event management (SIEM). Here’s how DNS monitoring compares with other monitoring techniques:

• Network Performance Monitoring (NPM): NPM tools focus on the performance and availability of networks and network components (like routers and switches). While NPM can identify network congestion and hardware failures that indirectly affect DNS services, DNS monitoring directly assesses DNS health, ensuring that domain name resolution processes are working as expected.
• Application Monitoring: This technique focuses on the performance and availability of specific applications. It can help identify issues within an application that may impact user experience but doesn’t directly monitor DNS processes. DNS monitoring complements application monitoring by ensuring that users can reach the applications in the first place.

Security Information and Event Management (SIEM): SIEM systems collect and analyze aggregated log data from various sources to detect and respond to security incidents. While SIEM can identify security breaches that may indirectly affect DNS services, DNS monitoring provides specific insights into DNS-related security threats, such as DNS spoofing or tunneling attacks.

Conclusion

So, now you know what DNS Monitoring is and why it is so important for your security. First, there are different criminal attempts that could be prevented when you keep an eye on your servers. Additionally, it is beneficial for simplifying the process of finding and fixing network issues. Finally, it helps you prepare and not be surprised in such situations.

The post Monitoring your DNS, should you do it? appeared first on ClouDNS Blog.

What is a DNS flood attack?

A DNS flood attack is a type of Distributed Denial of Service (DDoS) attack. It targets the DNS server, which is crucial for translating domain names (like www.example.com) into IP addresses that computers use to communicate. The attack floods the DNS server with an overwhelming number of requests, causing legitimate traffic to be delayed or completely blocked, effectively taking the service offline.

How does a DNS flood attack work?

Imagine a small post office suddenly receiving millions of letters, most with incorrect return addresses. A DNS flood attack operates similarly. Attackers leverage a network of compromised devices, known as a botnet, to send a deluge of DNS requests to a target server. These requests are often disguised with fake IP addresses, adding confusion and preventing easy filtering. The server, inundated by this tsunami of requests, struggles to respond, leading to legitimate requests being ignored or delayed – effectively disrupting normal web services. 

Let’s break down the process into steps:

1. Volume of traffic: The attacker sends a massive amount of DNS requests to the target server, often using a network of compromised computers (botnets).
2. Spoofing IP addresses: These requests often have fake return addresses, making it hard for the server to distinguish between legitimate and illegitimate traffic.
3. Server overload: The DNS server becomes overwhelmed, trying to process each request, leading to slowed down services or a total shutdown.
4. Secondary effects: The attack can also impact other services that rely on the DNS server, creating a ripple effect of disruption.

Why is it dangerous?

The danger of DNS flood attack cannot be overstated. They are more than just an inconvenience; they pose a significant threat to online operations. Firstly, they can cause major disruptions to essential services, crippling websites and online platforms. This disruption can have a cascading effect, impacting not only the targeted site but also any service that relies on it. The financial implications are equally severe, especially for businesses that depend on online transactions or services. Beyond the immediate financial losses, these attacks can inflict long-term damage to a company’s reputation, shaking customer confidence and trust. Moreover, while the focus is on mitigating the attack, other security vulnerabilities might be overlooked, leaving the door open for further exploits.

How to recognize a DNS flood attack?

Identifying a DNS flood attack primarily involves monitoring for an abnormal surge in DNS traffic. This is where tools like ClouDNS Free DNS tool come into play. This innovative tool enables users to inspect DNS records for specific hosts and analyze the speed and volume of DNS queries. Users can conduct a thorough audit of their DNS traffic, a crucial step in early detection. The tool’s user-friendly interface and comprehensive functionality, including compatibility with major DNS resolvers like Cloudflare, make it an invaluable resource in a cybersecurity toolkit.

DNS flood attack mitigation

To defend against DNS flood attacks, consider the following strategies:

DNSSEC (Domain Name System Security Extensions):

DNSSEC adds an extra layer of security by verifying the authenticity of DNS responses. This helps ensure that the data hasn’t been altered, making it harder for attackers to exploit the DNS system.

DDoS Protection Service:

DDoS Protection services specialize in distinguishing and mitigating abnormal traffic patterns characteristic of DDoS attacks. They can redirect malicious traffic, keeping your DNS server operational.

DNS Monitoring:

Regularly monitoring DNS traffic for unusual patterns helps in early detection of potential attacks, allowing for swift action before significant disruption occurs.

Enabling DNS Caching:

DNS caching reduces the load on servers by storing responses locally. During an attack, cached data can still be served, maintaining service availability for some users.

Secondary DNS:

A Secondary DNS provides redundancy. If your primary server is overwhelmed, the secondary server can maintain service availability, minimizing downtime.

DoT (DNS over TLS) and DoH (DNS over HTTPS):

Implementing DoT and DoH encrypts DNS queries, enhancing security. They help differentiate legitimate traffic from malicious queries, as most attack traffic doesn’t use these secure channels.

Conclusion

In summary, effectively mitigating DNS flood attacks involves a blend of strategic defenses and proactive monitoring. By adopting a range of protective measures and staying vigilant, organizations can safeguard their online presence against these disruptive threats. Remember, a robust defense is essential in maintaining the integrity and reliability of your digital services in today’s interconnected world.

The post DNS flood attack explained in details appeared first on ClouDNS Blog.