In Figure 1 below we demonstrate a single-flux network. We compare a normal web browser communicating directly with a typical website against the case of a single-flux service network, where the end user’s browser communication is proxied via a redirector (the ¨flux-bot¨ or ¨flux-agent¨). When a victim believes that they are browsing http://flux.example.com, their browser is actually communicating with the fast-flux service network redirector which redirects the requests to the target website. Single-flux service networks change the DNS records for their front end node IP address as often as every 3-10 minutes, so even if one flux-agent redirector node is shut down, many other infected redirector hosts are standing by and available to quickly take its place. We have found these fast-flux networks to be composed of primarily compromised home computers.
Fast-flux networks are responsible for many illegal practices, including online pharmacy shops, money mule recruitment sites, phishing websites, extreme/illegal adult content, malicious browser exploit websites, and the distribution of malware downloads. Beyond our regular observation of new DNS and HTTP services, other services such as SMTP, POP, and IMAP can be delivered via fast-flux service networks. Because fast-flux techniques utilize blind TCP and UDP redirects, any directional service protocol with a single target port would likely encounter few problems being served via a fast-flux service network.