No need to go through security again. The International Terminal is connected by a "tunnel" (actually it doesn't go underground) at the end of Terminal 3. Just exit your flight, go down to the main cross-hallway near the information desk and security, turn right and go all the way to the end. The passage to International is signed but takes a slight right turn just before you would exit a security point. Depending on which gate you come in at, it is 5 to 10 minutes at most. For the longer stretches, there are moving slidewalks.