How Does DNS Filtering Work?

Venture online and you will be faced with a wide range of threats, some of which could result in your bank account being emptied, others could see sensitive information being compromised and your accounts being hijacked. Then there is ransomware, which could be used to stop you from accessing your data (unless you have backups or pay the ransom).

More malicious websites are now being created than legitimate sites, so how can you stay safe online? One solution used by businesses and ISPs is a web filter. A web filter can be configured to restrict access to certain categories of Internet content and block the majority of malicious websites.

While it is possible for businesses, MSPs, and ISPs to purchase web filtering appliances that sit between end users and the Internet, DNS filters allow the Internet to be filtered without having to purchase any hardware or install any software. So how does DNS filtering work?

How Does DNS Filtering Work?

DNS filtering – or Domain Name System filtering to give it its full title – is a technique of blocking access to certain websites, webpages, and IP addresses. The DNS is what allows easy to remember domain names to be used – such as Wikipedia.com – rather than typing in very difficult to remember IP addresses – such as 198.35.26.96. The DNS maps IP addresses to domain names to allow computers to find web resources.

When a domain is purchased from a domain register and that domain is hosted, it is assigned a unique IP address that allows the site to be located. When you attempt to access a website, a DNS query will be performed. Your DNS server will look up the IP address of the domain/webpage, which will allow your browser to make a connection to the web server where the website is hosted. The webpage will then be loaded. The actual process involves several different steps, but it is completed in a fraction of a second.

So how does DNS web filtering work? With DNS filtering in place, rather than the DNS server returning the IP address if the website exists, the request will be subjected to certain controls. DNS blocking occurs if a particular webpage or IP address is known to be malicious. The DNS filter will use blacklists of known malicious websites, previous crawls of new websites and web pages, or web content will be assessed in real time if the web page or website has not previously been crawled and categorized. If the website trying to be accessed is determined to be malicious or otherwise violates pre-defined policies, instead of the user being connected to the website, the browser will be directed to a local IP address that displays a block page explaining why the site cannot be accessed.

This control could be applied at the router level, via your ISP, or by a web filtering service provider. In the case of the latter, the user – a business for instance – would point their DNS to the service provider. That service provider maintains a blacklist of malicious webpages/IP addresses and access to those sites is prevented.

Since the service provider will also categorize webpages, the DNS filter can also be used to block access to certain categories of webpages – pornography, child pornography, file sharing websites, gambling, and gaming sites for instance. Provided a business creates an acceptable usage policy (AUP) and sets that policy up with the service provider, the AUP will be enforced. Since DNS filtering is low-latency, there will be next to no delay in accessing safe websites that do not breach an organization’s acceptable Internet usage policies.

Will a DNS Filter Block All Malicious Websites?

Unfortunately, no DNS filtering solution will block all malicious websites, as in order to do so, a webpage must first be determined to be malicious. If a cybercriminal sets up a brand-new phishing webpage, there will be a delay between the page being created and it being checked and added to a blacklist. However, a DNS web filter will block the majority of malicious websites.

Can DNS Filtering be Bypassed?

The short answer is yes. Proxy servers and anonymizer sites could be used to mask traffic and bypass the DNS filter unless the chosen solution also blocks access to these anonymizer sites. An end user could also manually change their DNS settings locally unless they have been locked down. Determined individuals may be able to find a way to bypass DNS filtering, but for most end users, a DNS filter will block any attempt to access forbidden or harmful website content.

No single cybersecurity solution will allow you to block 100% of malicious websites or all NSFW websites. The purpose of a web filter is to reduce risk, not eradicate it entirely. Since the vast majority of malicious web content will be blocked, risk can be significantly reduced and there will only be a low chance of a website being accessed that violates your policies.

WebTitan Cloud from TitanHQ

WebTitan Cloud is a powerful, easy to implement DNS filtering solution that allows you to filter the internet and block access to malicious content and enforce your acceptable internet usage policies. Being DNS-based, there are no hardware requirements and no software downloads are required. To get started you simply point your DNS to WebTitan, set your filtering parameters through an easy to use web-based interface, and you will be filtering the internet in minutes. WebTitan Cloud can be used to protect users on and off the network, so it is the perfect choice for protecting remote workers from online threats as well as office staff.

WebTitan incorporates an intelligent AI-based component that provides real-time classification of websites for precision control over the content that can be accessed. WebTitan Cloud provides real-time categorization of over 500 million websites, and 6 billion web pages in 200 languages, including coverage of Alexa 1 million most visited websites. Industry leading antivirus is also incorporated to identify and block malware and ransomware threats. A full suite of reports gives you full visibility into the online activities of your employees and any guest users of your network. The reports can be scheduled or run on demand.

These and more features will allow you to block web-based threats and carefully control online activities for only a few dollars per user per year.

If you have yet to implement a web filtering solution, are unhappy with your current DNS filtering service, or you have questions about DNS content filtering, contact the TitanHQ team today and ask about WebTitan Cloud. We invite you to sign up for a free 14-day trial of the solution, including full support, to see for yourself the difference WebTitan makes.

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How Does DNS Filtering Work FAQ

What 3 things are most important about employee internet access?

Employees need internet access to complete their work duties, but it is essential to develop an acceptable Internet usage policy and get employees to sign it, that policy should be enforced using a web filtering solution, and you should have a sanctions policy for when employees violate the rules.

What is best, a web filtering appliance of cloud-based web filter?

Both options will provide clean, safe Internet access, but cloud-based web filtering does not require the purchase of a costly appliance, it is more flexible and scalable, and there is no patching burden. For SMBs and MSPs, cloud-based web filtering is the easiest and most cost-effective Internet filtering solution.

Does web filtering slow Internet speed?

Some web filtering solutions involve a degree of latency, but a DNS filtering solution will not slow internet speed as all filtering takes place at the DNS lookup stage of a web request before any content is downloaded. Filtering occurs in the same time as it takes to perform a standard DNS lookup so there is no latency.

How can I provide DNS filtering as a managed service as an MSP?

With WebTitan, adding web filtering to your service stack couldn’t be easier. WebTitan is can be set up in minutes, APIs allow easy integration into your existing back office systems, you will be provided with a white label version ready to take your branding, and you can even host the solution in your own environment.

How much does web filtering cost?

There is considerable variation in price between different web filtering solutions. The most expensive solution will not necessarily be the best option for your business. Price depends on contract term, the number of users, and add-ons. TitanHQ’s DNS filtering solution, WebTitan, typically costs around $1 per user, per month.