One of the most active threats we face today on the Internet is cyber-crime. Increasingly capable criminals are constantly developing more sophisticated means of profiting from online criminal activity. This paper demonstrates a growing, sophisticated technique called fast-flux service networks which we are seeing increasingly used in the wild. Fast-flux service networks are a network of compromised computer systems with public DNS records that are constantly changing, in some cases every few minutes. These constantly changing architectures make it much more difficult to track down criminal activities and shut down their operations.