Surveillance is easy, it does not require any special equipment and for little bit of money you can do a lot. Here is article analyzing Le Monde's article that talks about tracking of daily movement of French police and military. What can you do about it? Start deleting advertisement ID, may not help much but it's a good first step. I wrote about that in my mini advent calendar for privacy improvement on punkprivacy.com. Here is article itself: https://proton.me/blog/ad-tech-privacy #punkprivacy