Unit42 of Palo Alto Networks has been at it again. This time, they are looking at newly registered domains (NRD) and their propensity for delivering malicious malware.
Their post explains why NRDs should matter to the security community. "Our analysis," they say, "shows that more than 70% of NRDs are 'malicious' or 'suspicious' or 'not safe for work.' This ratio is almost ten times higher than the ratio observed in Alexa’s top 10,000 domains. Also, most NRDs used for malicious purposes are very short-lived. They can be alive only for a few hours or a couple of days, sometimes even before any security vendor can detect it. This is why blocking NRDs is a necessary, preventive security measure for enterprises."
Palo Alto defines NRDs as any domain that has been registered or had a change in ownership within the last 32 days. Its analysis indicated that the first 32 days is the optimal timeframe when NRDs are detected as malicious.
Time-variant instantiations should always be a red flag for a sysadmin. But with an NRD total volume that fluctuates between 150,000 and 300,000 a day, some instantiations can be missed in-between system scans.
NRDs are also associated with the distribution of malware. The Emotet malware family can serve an example. Emotet is a banking trojan well-known for sniffing network traffic for banking credentials. First discovered in 2014, it remains widely prevalent today.
Palo Alto says in the post that they have observed 50,000 unique samples at this point in 2019. The initial delivery is typically done through a phishing email or from a compromised website. This poisoned attachment often act as a downloader for a payload which is then executed to create the trojan. The downloading is performed via HTTP. Many of the URLs for the trojan were found to be hosted on NRDs.
Phishing campaigns can also routinely use NRD URLs in moving their data about.
A domain generation algorithm (DGA) is a common approach used by many malware instantiations to periodically generate a large amount of domains. These can serve malicious purposes like command and control and data exfiltration. Most DGAs generate domains based on the date and the time. The idea is to make a law enforcement takedown harder to implement by making the range of targets more random. The attackers will only have to register a few of the ones that have been created for their criminal uses. But they will show up as an NRD.
Palo Alto Networks recommends blocking access to NRDs with URL Filtering. Some may think it's aggressive due to potential false-positives, but they say that the risk from threats via NRDs is much greater. At the bare minimum, if access to NRDs are allowed, then alerts should be set up for additional visibility.
— Larry Loeb has written for many of the last century's major "dead tree" computer magazines, having been, among other things, a consulting editor for BYTE magazine and senior editor for the launch of WebWeek.