Fast flux

Fast flux is a domain name system (DNS) based evasion technique used by cyber criminals to hide phishing and malware delivery websites behind an ever-changing network of compromised hosts acting as reverse proxies to the backend botnet master—a bulletproof autonomous system. 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 fundamental 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 resource records, thus the authoritative name servers of the said fast-fluxing domain name is—in most cases—hosted by the criminal actor. Depending on the configuration and complexity of the infrastructure, fast-fluxing is generally classified into single, double, and domain fast-flux networks. Fast-fluxing remains an intricate problem in network security and current countermeasures remain ineffective. Fast-fluxing was first reported by the security researchers William Salusky and Robert Danford of The Honeynet Project in 2007; the following year, they released a systematic study of fast-flux service networks in 2008. Rock Phish (2004) and Storm Worm (2007) were two notable fast-flux service networks which were used for malware distribution and phishing. A fast-flux service network (FFSN) is a network infrastructure resultant of the fast-fluxed network of compromised hosts; the technique is also used by legitimate service providers such as content distribution networks (CDNs) where the dynamic IP address is converted to match the domain name of the internet host, usually for the purpose of load balancing using round-robin domain name system (RR-DNS). The purpose of using FFSN infrastructure for the botnets is to relay network requests and act as a proxy to the backend bulletproof content server which function as an "origin server".