Was driving by O'Hare on 8/25 and at the entrance to the south cargo area off Irving Park there was what I believe to be a roadside safety check. Every single vehicle was being stopped and when I passed around 5:15p there were at least 15 cars/trucks lined up. This involved Customs,ICC Police & DOA Police. A DOA officer even stopped someone exiting the airport. I quickly turned on the airport public safety TRS and heard the DOA officer say that his stop was part of oper. Viper - anyone know if this was a regular operation or something special.