First of all, Stalin was famous for rounding up citizens of Russia in the dead of night and murdering hundreds of them at a time in deserted areas. This is reflected in the Oceanic policy of "vaporizing" dissident citizens.
Orwell created the figure of Big Brother to reflect the totalitarian governments of the time period (1948) such as Franco, Mussolini, Stalin, Hitler, and Mao. All of those leaders, like Big Brother, ruled through the use of violence, control, and propaganda.
Another similarity between 1984 and the global reaction to communism is in the pressure placed on Oceanic citizens to betray friends and co-workers to Big Brother. The paranoia that characterized the McCarthy era in the United States was similar to the paranoia in 1984. People were actually being pressured to betray their friends, co-workers, and even parents in order to save themselves.