after going through customs, do you have to go back through security in order to make a connection?

It depends on the airport. If the airport has entirely separate terminal buildings for international and domestic flight, then yes. But some are connected so no.

In the past two years when returning to the US from China once and Mexico twice, I have cleared customs and immigration and had to go through security again each time. Each time I've taken my luggage to a dropoff point outside customs and then proceeded to the terminal or gates to board the connecting flight. So based on my personal experience, I would say that you would have to go through security again. On my recent trip to Mexico, I took a small backpack on the plane. I took along a plastic bag like a small shopping bag into which I put my coins, wallet, pens, belt, shoes, and anything else I had with me. Then I placed my shoes and the bag in the backpack to pass through the scanner. That keeps everything together and lessens the chance of something getting lost. If you have a light jacket you have to remove, you might consider tying the sleeves through the backpack. My girlfriend lost her jacket on our recent trip to Mexico. The lady from security reviewed the films and saw where the jacket was given to a lady in a wheelchair but by then it was too late to do anything about it as we needed to go to our gate to catch the flight to Mexico. Take care and have a good trip. As for me, I just try to not get too upset with the process and do what I have to do to arrive at my destination.