To be clear for anyone who might not want to read the whole article but also doesn't want to rely solely on the headline:

This isn't some new surveillance system that was revealed, or even really unprecedented tactics. This was just a larger number of HSI agents assigned to tracking activists, infiltrating meetings and chats, etc than the number previously assigned to investigate suspected foreign influence on the "New Left" and anti-Vietnam War movement. (which had 42 officers at its peak, vs the Minnesota 15 case having 119)