What steps have been taken by common free software OS distributions to protect against it? What can Windows users do? What ways are there to rid a system of it?
Look for the string "FinSpy" across all files.
"But their most intriguing finding was a small but telling word embedded in the spyware’s code: “FinSpy.”
That quote is from the article at http://bits.blogs.nytimes.com/2012/08/31/how-two-amateur-sleuths-looked-for-finspy-software/
According to that article you could also look for connections to servers answering manual connection attempts with Hallo Steffi".