The ex head of the Russian anti doping organization has come out and described in detail the way the Russians cheated during the Sochi Olympics. Acting on government directions Russian officials were under severe pressure to demonstrate Russian dominance at the Winter Olympics.
Russian secret service and police helped design a still secret method to break into the tamper proof bottles used to collect and store samples for testing. For Russian athletes that won a medal - at night the bottles with their samples would be secreted out of the secured room through a hole in the wall, bottles broken into and samples replaced with clean urine.
This method allowed Russian athletes to dope with a three drug cocktail throughout the games.
The allegation is that this was the reason that Russia won 33 medals, 10 more that at Vancouver, and dominated the medal count.
New York Times (paywall) broke this story and is continuing to run follow up stories:
http://www.nytimes.com/2016/05/13/sp...2014.html?_r=0
http://www.cbc.ca/sports/olympics/wi...port-1.3579290
http://www.cbc.ca/news/world/wada-ru...ndal-1.3580209