Malware writers and criminals have been using shared hosting platforms and so-called bulletproof hosting providers as bases of operations for their online crimes. As law enforcement agencies and security experts have moved to take these providers offline, the criminals have begun setting up their own virtual data centers. The criminals will buy servers and place them in a large data center and submit an application for a large block of IP space. In some cases, applicants are asked for nothing more than a letter explaining why they need the IP space, security researchers say.
Source: https://threatpost.com/attackers-buying-own-data-centers-botnets-spam-122109/73284/