It is my understanding that plenty of people do not believe North Korea cheated in 2010 (and also, plenty of people believe that other specific teams have cheated in specific years). Furthermore, it is my understanding that the North Korean team leader in recent years has not seen the problems before the contest (relying instead on the South Korean translation of the problems), thus removing the most obvious mechanism of cheating. Unfortunately, I do not know of a public source of this information and accordingly I have not verified it myself.
It is my understanding that plenty of people do not believe North Korea cheated in 2010 (and also, plenty of people believe that other specific teams have cheated in specific years). Furthermore, it is my understanding that the North Korean team leader in recent years has not seen the problems before the contest (relying instead on the South Korean translation of the problems), thus removing the most obvious mechanism of cheating. Unfortunately, I do not know of a public source of this information and accordingly I have not verified it myself.