FIFA are planning to freeze blood and urine samples of major players at the World Cup finals to discourage them from taking drugs. They are designed to keep players wary of the consequences of taking performance enhancing drugs. As time goes on, more advanced forms of detection will be invented and the samples will be tested. One of the goals FIFA has is to maintain a clean, drug free image for soccer.
http://www.espnfc.com/news/story/_/id/1796908/fifa-announce-new-anti-doping-protocol-advance-2014-world-cup-brazil?cc=5901