DNS tunneling is a difficult to detect attack that it transfers data from victim to attacker or
attacker to victim through DNS servers by the help of the malware. This data can be a sensitive
data that attacker want to steal like credit card information. It can be a command attacker want to
execute on the victim machine. Or even it can be used for downloading dangerous scripts or
applications
Therefore; DNS tunneling tends to rely on the external network connectivity of the
compromised system or DNS tunneling needs a way into an internal DNS server that has network
access. Attackers also have to control a server and a domain that may function as an authoritative
server to carry out data payload executable programs and server-side tunneling.
Impact of DNS Tunneling
DNS was first created for name resolution rather than for data exchange, thus it’s often not
viewed as a risk for data exfiltration or malicious interchanges of information. Most organizations
focus their security efforts on web and email traffic, as they see this as a regular source of attacks.
As a result, DNS is often overlooked. The threats posed by DNS tunneling exploits include:
DNS tunneling exploits may provide attackers with an accessible backchannel to exfiltrate
stolen information. DNS provides a covert means of correspondence to bypass firewalls.
Cybercriminals tunnel different sorts of protocols, such as HTTP or SSH, with DNS, which
allow them to covertly pass stolen data or pass IP traffic.
The DNS tunnel may be used as a full controller channel for an inside host that has already
been exploited. This allows cybercriminals to download code to malware, secretly take
records out from the organization, or have complete distant entry to the servers, and more.
DNS tunnels can also be used to sidestep captive portals, so they don’t need to pay for wifi services.
DNS tunneling uses the DNS protocol to tunnel information and malware via a clientserver model.
How DNS Tunneling Works
DNS tunneling makes use of the DNS protocol for tunneling malware and different data via a
client-server model. This typically involves the following steps:
The cybercriminal registers a domain, for example dangeorus.com. The domain’s name
server directs to the cybercriminal’s server, where the tunneling malware software is
installed
The cybercriminal infects a computer with malware, which penetrates the organization’s
firewall. DNS requests are always permitted to move in and out of the firewall, so the
infected computer is permitted to send queries to the DNS resolver. The DNS resolver then
sends requests for IP addresses to top-level and root domain servers.
The DNS resolver routes queries to the cybercriminal’s server, where the tunneling
program is implemented. A connection is thus created between the cybercriminal and the
victim via the DNS resolver. The attacker can use this tunnel for malicious ends, such as
exfiltrating information. There is no direct connection between the cybercriminal and the
victim, so it is harder to trace the cybercriminal’s computer.
Best Ways to Detect and Prevent DNS Tunneling
Detecting DNS tunneling involves various methods;
Anomaly detection entails monitoring DNS traffic for deviations from normal
behavior, such as unusually large data or excessive requests.
Payload analysis involves scrutinizing the content of DNS queries and responses,
but it can be resource-intensive and struggles with encrypted payloads.
Rate limiting restricts the number of DNS queries from a source within a specified
time, slowing down tunneling but not preventing it, with the drawback of potential
interference with legitimate traffic.
Intrusion Detection Systems (IDS) use security software to monitor network
traffic for malicious activity, including patterns indicative of DNS tunneling, but
they have limitations and can produce false positives
DNS monitoring tools combine multiple methods for a more comprehensive
approach, although they require expertise for effective use.
Implementing DNS Security Extensions (DNSSEC) is good to use against DNS
tunneling because uses digital signature to verify the authenticity of data, prevent
spoofing and other DNS based attacks.
Employing firewall rules is an effective strategy, as they can restrict outgoing
DNS traffic to authorized servers and inspect/filter DNS packets for suspicious
activity.
Regular patching and updates across systems, software, and network devices are
essential to safeguard against vulnerabilities that could be exploited for DNS
tunneling attacks, ensuring a robust defense against potential threats.
