This blog was written by Charlie Feng.
Over the years, McAfee researchers have observed that certain new top-level Domains (TLDs) are more likely to be abused by cyber criminals for malicious activities than others. Our investigations reveal a negative relationship between the likelihood for abuse and registration price of some TLDs, as reported by the McAfee URL and email intelligence team. This means that new TLDs are more likely to be picked up by cyber criminals if their registration prices are low.
What is a Top-level Domain?
According to Wikipedia, a top-level domain (TLD) is one of the domains at the highest level in the hierarchical Domain Name System of the Internet. It is the last part of the domain name, e.g. the TLD for www.google.com would be ‘com’.
There are two major types of TLD; country code TLD and generic TLD. The first type of TLD utilizes country codes directly, e.g. co.uk for the United Kingdom, and domains resolving to this type of TLD often have a strong tendency of serving those countries. Generic TLDs typically serve more general content and they form the basis of this study as they represent most of the domains we have observed recently.
TLD Registration Price
As noted by a previous article published by McAfee that bad hackers hack to make financial gains, there is no doubt that when cyber criminals plan to conduct malicious activities they will choose the method with the lowest cost to maximize their potential profits.
Below is a list of badly abused TLDs received from the McAfee URL and email intelligence team. Referencing domain.com, we found the one-year registration prices (domains created for malware attacks usually have a short lifespan as they are event-driven; normally they are taken off after the attack is stopped so they are registered for only one year, which is the minimal registration period required by many domain registration platforms, and that is why registration price is chosen for this study) for these abused TLDs are relatively low (under $20 for the first year) in comparison to other generic TLDs on the same list, which suggests that cost is a deciding factor.
To investigate that there is a possible relationship between TLD registration price and abuse rate, we investigated TLDs from different registration price ranges, from $1 to $270, and the results can be seen in the diagram below. The ‘abuse rate’ mentioned in the diagram is the number of domains under a specific TLD that are marked as either Medium or High Risk by McAfee which are normally blocked at endpoints, divided by the total count of the domains under the same TLD logged in McAfee’s URL database.
We can see that, as TLD registration price goes down, especially when it dips below $20, the abuse rate soars up. This seems to suggest a correlation between price and abuse. Looking at the diagram, although the trend is clear, there are several anomalies. To the left of the diagram we have ‘.BEST’, while to the right we have ‘.HOST’, ‘.LINK’ and ‘.SALE’ for outliers.
A reason for ‘.BEST’ being an outlier could be because, firstly, we do not have many domains under this TLD, so it is possible that the result is skewed due to insufficient samples and, secondly, its lexical feature makes it a really good TLD for marketing domains, especially ones driven by spam activities, even though the registration price is on the higher side. For the other outliers the reasoning is not so clear. It may be that their lexical features skew them closer to the legitimate side of things in comparison to the rest of the badly abused TLDs. Nonetheless, they still have abuse rates greater than 20%, so they are still badly abused if you compare them to the ones to the left of the diagram.
While conducting the above study we also considered the percentage of domains under these badly abused TLDs that are ranked among the highest trafficked websites, as reported by services such as Amazon Alexa. A study on the below six TLDs, which our email intelligence team report as being highly associated with spam activities, was carried out.
It can be seen from the chart above that for the domains under these six sample TLDs, the average percentage of Alexa top 1 million websites is below 1%, which reinforces the fact that these TLDs do not typically serve much legitimate content. Organizations may want to evaluate these findings and based on their risk appetite undertake further scrutiny on the domain of inbound and outbound traffic. The level of scrutiny undertaken on the originating source very rarely considers the price of registering a domain, and whilst such an approach may not be sufficient to warrant such analysis for many organizations, those with a low risk appetite may want to consider such action.
Advice to our customers
Different customers of McAfee’s have different security policies towards their endpoints which in turn supports their overall risk appeitite.. In regards to the graph depicted above different approaches might be taken on these TLDs that tend to be considered ‘too risky’. if enterprise customers would like to avail of this function, it can be easily achieved by adding a local rule in the McAfee Web Gateway Configuration Panel.
At the same time, for other organizations with a higher risk appetite, such aggressive approach might not be needed. Whatever the final action might be however, it is always good to review the security policies from time to time for your organization and consider what kind of policies would suit your business the best.
Meanwhile, to our Web Advisor customers, we would like to suggest that whenever you receive any URLs that resolve to the risky TLDs mentioned above, if it has a Unverified / Medium / High Risk reputation and/or it does not have any categories in McAfee’s database (which can be double checked at https://trustedsource.org), then please be wary of clicking on those URLs as they may pose a greater security risk to you.
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