Using DNS to bypass network controls – DNS tunneling
Often in organizations, outbound access is not allowed or is allowed only via HTTPS via proxy servers. But regardless of how strict the firewall rules and Access Control Lists (ACLs) are set, DNS requests are usually allowed through the firewalls. Attackers can abuse these misconfigured DNS service rules by creating a tunnel directly through compromised workstations or servers to exfiltrate confidential data to their servers, hosted externally on the internet.
This approach is similar to other tunneling protocols such as HTTP, HTTPS, TCP, and so on, but here, the protocol is DNS and the transmission channel is UDP.
To create a tunnel, we need a handler and a DNS server to communicate from the internal network of the organization and exfiltrate a good amount of data, without missing a single packet because of congestion or connection breaks in between and without getting detected. To achieve this, there are numerous...
