What security agencies are affected by the shutdown?

I could be wrong, and I haven't bothered to do any research, but among the misconceptions about a government shutdown is that every single thing is closed. Not true at all. Things considered essential, such as the Secret Service, the TSA, the military, and the like keep operating. Federal prison guards will still be on duty. Social Security payments will still go out. For what it's worth, they've long since gone to only electronic deposits, which probably makes it a whole lot easier to keep sending them out, as compared to the old paper checks.