The Black Hole exploit kit, is one of the most popular platforms for infecting users with malware. Developed in Russia, it is available for rental by anyone who wants to install their "software" on unwitting people. Technical support is even provided for the rental customers. Technologically, the exploit kit has two primary functions: 1. Statistics tracking and reporting on the browser configurations of unwitting visitors. 2. Exploiting IE, Java, Flash, or Acrobat to drop and execute an arbitrary EXE on someone's Windows system.
This exploit kit was recently in the news again, because of the release of the "totally rewritten" version 2.0 -- which is actually not really that different from version 1.2.5 released two months before.