One of the most popular methods used by companies and providers to protect their environments from online dangers is DNS filtering (aka DNS blocking). Instead of utilizing nine-digit IP addresses, users can access websites utilizing domain names such as heimdalsecurity.com. Domain Name System filtering is a method of preventing access to questionable, shady, or harmful domains. Whenever a user attempts to enter a domain, a blacklist of malicious domains or IP addresses is checked; if a match is found, the domain won’t be resolved, therefore access will be denied. To that end, DNS can be employed to restrict access to particular sites. Numerous businesses believe that using this method will increase both security and productivity.

How Does DNS Filtering Work

A user who opens a phishing link in a fake email, for instance, will automatically be sent to a malicious website that may steal login credentials or distribute malware. Yet, the threat would be immediately stopped if this particular domain was blacklisted in the DNS resolution service.

When DNS filtering is implemented, the request will be open to some constraints instead of the DNS server returning the IP address if the site exists. DNS blocking happens when a specific website or IP address is recognized as harmful. The DNS filter will make use of blacklists of websites that are known to be dangerous, past crawls of new websites or web pages, or real-time evaluation of web content if the website or web page has not yet been crawled and categorized. Rather than connecting to the website, the user’s browser will be sent to a local IP address that shows a block page outlining the reasons why the website cannot be accessed because it is harmful or otherwise violates pre-established policies.

DNS filtering

The restriction could be implemented at the router level, through your Internet provider, or by a company that offers web filtering services. In the second scenario, the client—say, a company—would redirect their DNS to the ISP. As a result, access to websites on this service provider’s blacklist of harmful websites and IP addresses is restricted.

Additionally, DNS filtering can be used to restrict access to specific categories of sites, such as pornography, file-sharing portals, gambling, and online gaming sites, since the ISP will also categorize web pages. The acceptable usage policy (AUP) will be implemented if a business develops the AUP and integrates it with the service provider. Because DNS filtering has a fast response time, accessing secure websites that adhere to a company’s authorized Internet usage standards will be almost instantaneous.

Nevertheless, no DNS filtering solution can completely block harmful sites because doing so requires first determining whether a particular website is dangerous. There will be a lag time between when a malicious user pulls up a new phishing webpage and when it is verified and added to a blacklist. Still, the bulk of harmful websites will be blocked by a DNS web filter.

A web filter’s aim is to lessen the risk, not completely eliminate it. Risk can be considerably decreased and there will only be a small chance that a domain will be reached that is in violation of your policies as the overwhelming majority of dangerous web content will be prevented.

DNS filtering can aid in preventing malware, or harmful software, from entering corporate networks and personal devices. It can also assist in thwarting specific phishing campaigns.

But how exactly does DNS filtering safeguard against malware and phishing attacks?

1. It blocks compromised websites

A site that contains malware may try to deceive users into installing a dangerous application or may carry out a drive-by download (an instantaneous download of malicious software that occurs as soon as the webpage opens). Several other threats are also feasible. As a comprehensive programming language, JavaScript is used to run code on websites and can be used in a variety of ways to corrupt consumer devices.

By preventing users from ever loading malicious URLs, DNS filtering can stop these kinds of intrusions.

2. It blocks phishing websites

A phishing website is a phony website created for the purpose of phishing attacks to collect user credentials. The used domain might be a fake one or just one with an official appearance that most users won’t acknowledge. The objective is to trick the user into providing their login details to a hacker, regardless of the strategy used. DNS filtering can be used to prevent access to these websites.

These capabilities rely on the DNS filtering system’s ability to recognize illegitimate IP addresses and domains. DNS filtering can stop this harmful behavior, but cybercriminals constantly create new domains, making it impossible to blocklist them all.

When it comes to DNS content filtering some filters use default operations and others are administrator-controlled. Among them, we mention: 

  • Category filters: Category filters allow administrators to block access according to the nature of the websites’ content (for example racial hatred, pornography, etc.)
  • Keyword filters: Keyword filters allow blocking access to certain websites or web applications by specific words found in the websites’ content (here we mention “chat” or “Netflix, for example). 
  • Administrator-controlled Blacklists and Whitelists: Blacklists and Whitelists offer personalized DNS content filtering since access to specific websites is entirely determined by the administrator.

How Can DNS Filtering Benefit Your Business? 

Regardless of how many security precautions you implement and how much training you provide to staff members, accidents can still occur, endangering the devices and network of your organization. The default level of cybersecurity for a business can be strengthened with efficient DNS filtering. It is possible to stop the overwhelming majority of threats, despite the fact that there is no method to ever totally eliminate the possibility of an employee connecting to a malicious website because malicious actors are constantly producing new web pages that have not yet been analyzed and flagged, giving them a better chance of slipping through.

DNS filtering can help you prevent malware, ransomware, and phishing attacks. Moreover, it can help increase productivity, reduce HR issues and ensure a safer browser experience. 

What type of DNS attacks can you expect if you’re not using a DNS filtering solution? 

When it comes to the types of attacks your company can become the target of,  you should know that there are dozens of possible threats that can get into your organization in the blink of an eye, anytime and anywhere, causing you to lose money, data, and time. 

  • Subdomain attacks: Attackers could try to overload authoritative name servers with queries for unexistent subdomains (111aaa.example.com instead of example.com, for instance), consuming its resources and causing disruption to legitimate queries. 
  • Cache poisoning: Cache poisoning attacks aim to corrupt the recursive servers, more specifically the answers stored in the cache. If they succeed, any subsequent query will get the corrupted answer. 
  • Phantom Domain: Phantom Domain attacks also involve authoritative servers and imply asking for non-existent recursive name servers, which wastes the server’s time and fills up the cache with useless answers. 
  • Malware: Hackers need to maintain communication in order to make a profit, and one certain way of obtaining it is through DNS. Malware uses DNS to communicate with the command-and-control server, but also to update itself, like the famous WannaCry ransomware
  • Hijacking and redirection: In this type of attack, users are sent to a different destination than they intended. Similarly, the target client machine could be infected with malware that would allow all DNS requests to be sent to the DNS server under the attacker’s control. 
  • Data exfiltration/tunnelingTunneling involves encoding messages in DNS queries and answers in order to avoid detection. Tunneling can be used for legitimate purposes, but also to exfiltrate sensitive data, in which case the ever-changing domain names make it very hard to detect. 

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How Can Heimdal® Help?

One of the four levels of security the Heimdal® products are built on is prevention. In order to help you achieve unique threat prevention, we propose two main modules: Heimdal Threat Prevention Network and/or Heimdal® Threat Prevention

Heimdal® Threat Prevention Network is a powerful Intrusion Prevention System that protects your organization’s network at the perimeter level, preventing, detecting, and blocking ATPs, ransomware, data leaks, and network malware. It prevents command and control server connections, logs network traffic, checks who is doing what, and tracks the history of threats that were unknown but become known. Heimdal® Threat Prevention Network also offers you, of course, the possibility to use custom block pages and to allow/blocklists. 

Heimdal® Threat Prevention Network is compiled of two Heimdal trademarked engines, DarkLayer Guard™  and VectorN Detection™.  DarkLayer Guard™ offers full DNS protection, as well as active and passive modes and full network logging, while VectorN Detection™ uses Neural Network Transformed AI for tracking device-to-infrastructure communication to spot and stop attacks that firewalls cannot see. 

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Heimdal® Threat Prevention adds to all this the power of the Heimdal® Patch & Asset Management​, our patch management solution for Windows and 3rd party software. Since 85% of malware is deployed through exploit kits, automatically installing updates only 4 hours after the release or scheduling them according to the PC’s clock and having an in-app software center would make nice touches to your company’s cybersecurity. 

With Heimdal® Threat Prevention you would benefit from a solution that closes vulnerabilities, helps you be GDPR compliant, and adds unique threat hunting, prevention, and detection for stopping ransomware, APTs, financial fraud, data leaks, and exploits. 

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Wrapping Up…

You need to take cybersecurity seriously and you need to start adopting security measures right now – and a professional DNS content filtering solution is your best chance to protect your business against up to more than 90% of the possible (and very probable) threats.  

Whatever you choose, you should remember that Heimdal® always has your back and that our team is here to help you protect your home and your company and to create a cybersecurity culture to the benefit of anyone who wants to learn more about it. 

Drop a line below if you have any comments, questions, or suggestions – we are all ears and can’t wait to hear your opinion!

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