The National Cyber Security Centre, a part of the UK's GCHQ, has issued an advisory that deals with Domain Name System (DNS) hijacking by threat actors.
DNS hijacking refers to the unauthorized alteration of DNS entries in a zone file on an authoritative DNS server (or the modification of domain configurations in relation to a domain registrar) by an attacker. This can be used to redirect traffic in order to capture sensitive information.
The NCSC has recently observed various attacks which exploit the DNS system at different levels. This includes the "Sea Turtle" bad actors which have been plaguing Brazil. Avast has discovered that 180,000 users in the Avast user base, located in Brazil have had their DNS hijacked in the first half of 2019.
A threat actor using this method can create malicious DNS records. These records can hide a malicious site within an organization's familiar domains. The camouflage can help hide a phishing site, for example.
Domain-validated SSL certificates are issued based on the creation of DNS records; so an attacker may obtain valid SSL certificates for a domain name, which could be used to create a threat website.
An attacker could carry out transparent proxying with this method. This is when the attacker modifies an organization's configured domain zone entries (such as "A" or "CNAME" records) to point traffic to their own IP address (which would be infrastructure that they manage).
The NCSC has a number of mitigation techniques that they recommend.
For instance, they have found that the most common DNS hijacking takes place at the registrar level, simply by gaining unauthorized access to a registrant's account. This is usually done by the standard kinds of methods like phishing, credential stuffing and social engineering.
They recommend deploying Multi-Factor Authentication (MFA) when available.
Other preventative methods can be taken, as well. An organization can regularly audit who can access the registrar control panel and make changes with the registrar. Controlling legitimate access to the registrar is a very important step.
Another important, but often overlooked step, is realizing that domain registrations typically have four points of contact: the registrant, technical, administrative, and billing contacts. An organization must ensure that all contact information is up to date. This is non-trivial, since contact updates are often overlooked when an organizations grows, shrinks, moves, or is acquired. A registrar may send certain types of communication to only one of those roles, and in some disputes, the registrant contact usually takes precedence.
Many registries offer a "registrar lock" service. This lock prevents the domain being transferred to a new owner, without the lock being removed. This is an additional level of protection whereby changes cannot be made until additional authentication has taken place which usually involves a call to the owner.
DNS can be an easy to exploit portal into your organization. Paying attention to the details of it rather than just assuming it will do things automagically is the only secure path an organization has.
— 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.