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How Do I Use the Domain Score to Determine Whether a Domain Is a Threat?

To be most effective, protective DNS services need to constantly reassess and rescore domains as additional data comes in.

Dave Mitchell

December 8, 2022

4 Min Read
Browser search bar showing an URL address made of fishing hooks. Illustration of web domain spoofing and email phishing
Source: Dragon Claws via Adobe Stock

Question: What is the importance of a domain score when determining whether a domain is a threat?

Dave Mitchell, CTO, Hyas: Did you know over 93% of all malware employs DNS as a mechanism to identify and contact its command and control (C2) to receive instructions? This is why a truly holistic cybersecurity strategy must include protection from malicious domains.

Being able to properly assess the reputation and safety of a particular domain is critical to preventing breaches. However, these results are often presented in terms of a threat scoring system, which can misleadingly imply static results. To be most effective, solutions in this space need to constantly reassess and rescore domains as additional data comes in. Legacy approaches to protective DNS fail to adapt to the inherently dynamic nature of the Internet. A proactive system must score potential threats in real time, categorizing the DNS traffic based on both static and dynamic indicators of malicious intent.

First, there are the known bad domains. These are domains that have been publicly reported and confirmed to be malicious. Blocking these domains is critical, but it is only a reactive measure. If your organization gets hit during the first wave of an attack that utilizes new malware or a new exploit, these static lists will not help. Using public block lists also leaves you open to attacks from known threats utilizing different infrastructure. Publicly known malicious domains are usually subject to the strictest layer of protection, and communication with them is forbidden. Someone would have to have a very good reason to access one of these domains.

More proactive scoring methods rely on assigning a threat category to all queried domains based on a wide variety of indicators. This is a huge advantage over the static approach, as detecting a threat in its early stages can give administrators the invaluable time they need to block domains involved with the attack before it is executed — thereby rendering it inert. For a solution to do this effectively, it requires advanced threat intelligence capabilities and an intimate understanding of attacker infrastructure and methodology to know how domains are being used and by whom.

Based on this information, advanced protective DNS services monitor domain traffic for suspicious indicators. For example, if a domain is brand new, bought from an unscrupulous registrar, purchased by a buyer from an area associated with cybercrime, and paid for in cryptocurrency, it's probably smart to block it — even if that domain hasn't been used in an attack yet. The number and severity of the suspicious indicators it finds will determine how the system classifies the domain. Sometimes the indicators are low-priority enough to permit communication with the domain, while still getting marked for further analysis. If the domain is later determined to be malicious, further communication will be blocked. Every service provider has its own secret sauce when it comes to scoring domains, so do your homework and demo a number of services before settling on one.

The more high-quality data a service has access to, the more accurate its results are likely to be when combined with continuous analysis. This is key for generating meaningful scores that maintain the delicate balance between overly aggressive blocking — annoying users and potentially slowing down the pace of business — or even worse, mistakenly letting malicious communication through, defeating the purpose of implementing the protection in the first place.

Beyond these built-in protections, administrators can usually set up custom lists or policies that make the system alert them and/or outright block DNS requests if a domain has multiple negative traits that meet or exceed established parameters. Once alerted, administrators can investigate the incident and proactively deal with it before it causes damage. An advanced protective DNS service also gives you a level of control in enforcing policies, as you can preemptively block certain DNS communications — for example, instituting a blanket block on certain hacker hotbeds. If clean traffic gets caught up in these custom rules, it is easy enough to add domains to the solution's allow list.

Every provider approaches the overall process of scoring domains differently — quite radically in some cases. Bare-minimum (sometimes free) protective DNS services often rely on static, publicly available lists, while more sophisticated services incorporate data from premium intelligence services to stay a bit more current. But the top options use advanced threat intelligence, based on examination of prior attacks and dynamic analysis, to predict domain risk. With the first two types, you are operating from a reactive stance and will almost certainly fall victim to an attack at some point. However, an advanced protective DNS helps secure your assets from new and emerging threats, giving your enterprise the upper hand against threat actors.

About the Author(s)

Dave Mitchell

CTO, HYAS

Dave is responsible for the technical vision at HYAS. His experience as both a team player and entrepreneur is first class. He helped build and secure web-scale networks, including TWTelecom, Yahoo!, and Twitter. He also founded Singularity Networks, which was acquired by Cisco in 2019.

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