The Domain Name System (DNS) is one of the least understood but most crucial parts of any IT environment. Although it’s operated via a global network of servers under the control of ISPs, non-profits, registries and others, attacks can strike to the heart of any organisation. DDoS, phishing, malware downloads, C&C communications and even data exfiltration can all take place via DNS channels.
Because it’s always on and running in the background, converting domain names to IP addresses so users can surf the web, it’s a great conduit for attackers. But that also makes it a useful place to gain advanced insight and control. I spoke to a range of industry experts on the key challenges and opportunities facing firms.
A new favourite
DNS attacks are becoming increasingly popular with nation state hackers. Sea Turtle and DNSpionage campaigns over the past couple of years have targeted Middle Eastern governments and military organisations. They typically compromise key DNS servers, and change the queries stored in them to enable man-in-the-middle phishing attacks designed to secretly steal important passwords. Part of the problem, according to Nominet’s head of IT security, Cath Goulding, is that the protocol is decades old.
“DNS was designed nearly 50 years ago. The people who created it could not possibly imagine the threats that we face today,” she tells me via email. “The advanced malware that we see could not be conceived 50 years ago, so DNS was not designed to defend against it. Humans simply can’t manually monitor the amount of data that passes through it, so we must rely on algorithms and machine learning to keep us safe.”
Gary Cox, technology director for Western Europe at Infoblox, adds that DNS is increasingly being targeted by hackers as other avenues are blocked.
“DNS has become more and more popular as a result of other security gaps being filled – by things like next-gen firewalls, IDS/IPS systems, highly capable endpoint protection going well beyond just basic Anti-Virus,” he explains to me. “New attack vectors are continually explored and exploited, and the latest twist from a DNS perspective is that DNS over HTTPS (DoH) is now being used to circumvent DNS security controls.”
According to DNS pioneer and Farsight Security CEO, Paul Vixie, services like DoH “are well intentioned but policy-ignorant, and many threats to the user or to the rest of the user’s network are able to bypass security controls when the user bypasses the local name service.”
Another example of a DNS bypass attack which has garnered an increasing number of headlines over the past year is DNS rebinding. In this attack, hackers first get victims to click on malicious links or online adverts, with rebinding techniques enabling them to bypass the network firewall and use the victim’s browser as a proxy to target any devices on this network. It’s predicted that this type of attack could become increasingly popular in compromising IoT endpoints.
What can we do?
So how can IT security leaders hope to mitigate the risk of a DNS-based attack? After all, with the DNS servers themselves usually out of their control, there’s a limit as to what they can do, right? Well, yes and no. Goulding argues that by using analytics services that search DNS traffic, organisations can turn the ubiquity of DNS to their advantage, using it as an early warning system to spot and block attacks before they’ve had a chance to impact the organisation.
“Utilising a DNS monitoring tool is the first step to mitigating the DNS risk,” she explains. “And while not every firm can afford high-level DNS protection, taking steps to ensure staff education is crucial, too. For many workers, they might not be clear what is and what isn’t a malicious link or malicious add. Ensuring staff have the tools they need to work out what might be malicious and what not be malicious will ensure company safety.”
ISACA board director, Asaf Weisberg, adds that DNSSEC should be rolled across the industry “to strengthen authentication in DNS, by using a DNS Zone’s private key to digitally sign the DNS data, and allowing the resolver to confirm the validity of the DNS data through a corresponding public key that is being retrieved as part of the DNS query.”
However, efforts thus far have been poor. It’s claimed that less than 20% of DNS stakeholders have adopted the specifications – a figure ICANN wants improving urgently. Without this kind of cross-industry response, DNS could remain a security blind spot for organisations for many years to come.