usenet index posts question

I have been away from newsgroups for quite some time, having moved to private torrent trackers when activity on my favourite newsgroups dropped off dramatically a couple of years ago. Today I decided to have another look at my favourite newsgroups to see what is happening there these days. To my surprise I now see lots of "Usenet Index Posts" followed by a long string of numbers. These did not exist when I was last using newsgroups. After a lot of online searching I understand that they are something to do with escaping surveillance from copyright enforcers, but beyond that I am totally in the dark. Can someone please explain to me what these files are, who can use them and how?

My usenet client is Newsleecher, along with its Supersearch facility.