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The Domain Name System (DNS) makes all the networking communications possible. DNS may seem like an invisible force or entity, until something goes wrong, then it is clear: If DNS service goes down, then nothing works.
Here are some best practices and the most important security measures to keep your DNS infrastructure safe and secure.
Ensure DNS Redundancy and High Availability
As DNS is the pillar of network applications, the infrastructure of DNS needs to be highly available. To obtain the essential redundancy, you need to have at least the primary and secondary DNS servers in your organization.
To keep the business-critical services running, you must have at least two internal DNS servers. All active directory, file sharing, and email services depend on proper DNS operation. Without healthy and functional internal DNS servers, there will not be any communication in internal devices.
If one DNS server runs into an error or an issue, the other one takes over the next step immediately. If the primary server is not responsive, automatically admins configure machines to use secondary DNS. An IP can be in any address within a private network IP range of an internal DNS server. By making DNS servers sacked, you can come up with a high availability of the DNS infrastructure.
Hide DNS Servers and DNS Information
Every DNS server and each piece of information will not be made accessible to all users.
If the individuals use these servers, first they must access the necessary servers and data. This is especially more important if your domain names need to be noticeable by the public.
The second thing is, Primary servers should not be visible to the external users, so you must hide your primary DNS server.
Finally, the primary servers must be in privacy, and it should be accessible only to the system admins and IT personnel. If you allow primary DNS servers visible and accessible to all internal users, that may become a significant security issue.
Use the Local or Closest DNS Server
Large organizations often have offices worldwide. You should set up a local DNS server in every office, if the infrastructure allows.
The reason is a local server brings down the response time for DNS requests. When a query travels across WAN to a remote name server, a user cannot load quickly, it takes a long time.
With a high number of clients, the number of DNS queries increases. One centralized set of DNS servers can handle all requests, but with more expectancy. By pointing users’ machines to a local or closest name server, response times will get reduced to a minimum.
In this case, latency will not exceed 50 ms. Moreover, the number is usually lower than the value. Using the closest DNS server, it brings up the load times for all machines. This way, you also take the burden off the remote server in HQ and prove its performance high.
DNS Security Best Practices
DNS servers are a repeated target of cyber-attacks. Securing DNS infrastructure is a crucial step in ensuring breaches into your organization. To avoid a major impact on your DNS setup, make sure to utilize the security measures given below.
Enable DNS Logging
DNS logging is the most efficient and useful way to monitor DNS activity. If someone is interrupting your DNS servers, the logs let you know. When there are any issues with DNS queries or updated, debug logs let you know the queries.
Even though DNS debug logging upgrades the security to a higher level, some system admins decide to break it. The main reason is to increase performance. Monitoring network activity can help you to stop some attacks, such as DDoS, but not cache poisoning.
Lock DNS Cache
Whenever there is a query from a client, DNS finds that information and stores it in the cache for future use. This process allows the server to respond faster to the same queries. Attackers can exploit this feature by changing the stored information.
The next step from enabling DNS debug logs is locking DNS cache. This feature confirms, when the cached data can be changed. The server keeps lookup information during the amount of time defined by the TTL (time to live). If cache locking is helpless, then the information can be overwritten before the TTL gets over. This ends in cache poisoning attacks.
Depending on the operating system, cache locking gets enabled by default. The cache locking scale goes up to 100 percent. When the value is set to 70, overwriting the data is not possible for 70% of the TTL. By defining cache locking to 100, changing the cached information is blocked until the TTL gets over.
Filter DNS Requests to Block Malicious Domains
DNS filtering is the most efficient way to ensure users from accessing a website or a domain. The main reason to block name resolution for a domain is known to be malicious. When a client sends a query for a blocked website, a DNS server automatically stops the communication between them.
DNS filtering massively brings down the chances of viruses and malware reaching your network. When a client is unable to reach a malicious page, the number of threats that can crawl inside your infrastructure is minimal.
Besides security, organizations, due to their business policy they may block the domain. The list of blocked domains consists of social media, gambling, pornography, video streaming pages, or any other website. DNS can filter requests by a user, a group, or block the access for every user.
Validate DNS Data Integrity with DNSSEC
Domain Name System Security Extensions (DNSSEC) allows clients to receive their valid responses based on their queries. Data integrity got success by DNSSEC digitally signing DNS data provided to nameservers. When an end-user sends a query, a DNS server provides a digital signature with the response. Hence, clients are in a safer hand that they received valid information for the request they sent.
Configure Access Control Lists
Access Control Lists (ACL) are another way of ensuring DNS servers against unauthorized access and spoofing attacks. Only IT administrators and system admins should have access to your primary DNS. Configuring ACLs to allow inbound connections to a nameserver from specific hosts will ensure that only the intended staff can communicate with your servers.
There is always a pathway for improvement in the DNS design and security based on your infrastructure. Constant threats are lurking and waiting to exploit vulnerabilities in your IT system. However, if you follow the points listed above, you will cover the most important aspects your DNS infrastructure needs to stay secure and safe.