Adversaries may use Fast Flux DNS to hide a command and control channel behind an array of rapidly changing IP addresses linked to a single domain resolution. This technique uses a fully qualified domain name, with multiple IP addresses assigned to it which are swapped with high frequency, using a combination of round robin IP addressing and short Time-To-Live (TTL) for a DNS resource record.(Citation: MehtaFastFluxPt1)(Citation: MehtaFastFluxPt2)(Citation: Fast Flux - Welivesecurity)
The simplest, "single-flux" method, involves registering and de-registering an addresses as part of the DNS A (address) record list for a single DNS name. These registrations have a five-minute average lifespan, resulting in a constant shuffle of IP address resolution.(Citation: Fast Flux - Welivesecurity)
In contrast, the "double-flux" method registers and de-registers an address as part of the DNS Name Server record list for the DNS zone, providing additional resilience for the connection. With double-flux additional hosts can act as a proxy to the C2 host, further insulating the true source of the C2 channel.
Detection Strategy for Dynamic Resolution using Fast Flux DNS
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