Fast flux is a DNS technique that has and continues to be used by botnets to disguise phishing and malware delivery sites behind an ever-changing network of compromised hosts acting as proxies. It can also refer to the combination of peer-to-peer networking, distributed command and control, web-based load balancing and proxy redirection used to make malware networks more resistant to discovery and counter-measures.

The basic idea behind Fast flux is to have numerous IP addresses associated with a single fully qualified domain name, where the IP addresses are swapped in and out with extremely high frequency, through changing DNS Records. Internet users may see fast flux used in phishing attacks linked to criminal organizations, including attacks on social network services.