A Domain Generating Algorithm (DGA) is a program or subroutine that provides malware with new domains on demand or on the fly.
Kraken was the first malware family to use a DGA (in 2008) that we could find. Later that year, Conficker made DGA a lot more famous.
What’s the use?
The DGA technique is in use because malware that depends on a fixed domain or IP address is quickly blocked, which then hinders operations. So, rather than bringing out a new version of the malware or setting everything up again at a new server, the malware switches to a new domain at regular intervals.
An example of DGA in practice is C&C servers for botnets and ransomware. If we were able to block these or take them down, we would cut the link between the victims and the threat actor. Bots would no longer be able to fetch new instructions and machines infected with ransomware would be unable to request encryption keys and send user data.
The constant changing of the domain for the C&C server is also sometimes called “Domain Fluxing” or “Fast Fluxing”, which actually is a reference to an older technique based on abusing the DNS load balancing system.
Read more in