South Korea's so much fort with numbers, that's the standard plan for the Mexico game.

In a world that has shown itself to be very balanced in the first few matches, little information about your opponent gives you priority. And this is where the spy network, which every team tries to use to the full. There is no exception to South Korea, which is the first group match [...]
And this is where the spy network, which every team tries to use to the full. There is no exception to South Korea, which lost its first game in the group to Sweden. Asians have documented this outcome and all attention has now focused on the next match, the one against Mexico on Saturday.
A group of Korean journalists have attempted to spy out the closed-door training of Americans-centers. Security near the tricolour team found that they were trying to register the private exercise of Osorio's team, 15 minutes after FIFA's permission for journalists ended. How were they able to avoid security? After completing the time of training with open doors, they sat in the café in front of the training center.
Once Koreans were spotted studying every detail of the opponent's training without consuming any drinks, the security staff went and drove them out of the restricted area. However, journalists realized that they had been discovered and rushed away before security accompanied them. A few days ago, the Korean coach changed the numbers to the players in training, just so the rivals did not know.