Most (but again, not all) airports connect international terminals airside. When you're connecting from an international flight to a domestic one, you'll always have to exit and reenter security as you'll need to go through customs and immigration (unless you have gone through preclearance aboard, which is rare).
Why did I get extra security at airport?
Being tagged with SSSS isn't the only reason you might have to undergo extra security processes, from pat-downs to hand swabs to bag searches. The most common reason you'll be picked for extra security is that during the bag scanning process, the TSA agent sees something they're unsure about.
Why do you have to go through security twice?
Do you go through security twice?
There is no other Airport Security check once you are already in the terminal, finding Boarding Gate. Yes you can – once you clear security, nothing is stopping you from leaving the secure area and then going through again. In some circumstances, you have no choice about going through security twice.
Do I have to go through security again for layover?
For domestic-to-domestic layovers, you normally won't have to go through security again during your layover. However, for all international layovers, you will normally have to go through security again, but this will depend on individual airport policy.
What does it mean if you have SSSS on your boarding pass?
Secondary Security Screening SelectionGetty. An SSSS code on a boarding pass stands for “Secondary Security Screening Selection.” While somewhat of an annoyance, this code only means you have been flagged to undergo additional security screening procedures.