I got the SSSS in September for my flight from GIG to MIA. I only got the SSSS for my boarding pass for this leg of the trip, not for my next leg from MIA to ORD.

I was told that the airline selects some people for this and that it only happened for US carriers. I asked whether people also who flew TAM also received the extra screening and I was told that no, TAM customers were not selected for this.