Minutes after sharing a file this morning, I received an email from my Internet Service Provider, Xfinity, saying they received a "Copyright Violation Notice" that someone downloaded a copyrighted video from me (citing the exact filename) and asked me to delete the file.

I've NEVER received a notice like this before and it is concerning that Xfinity might be monitoring my traffic (down to the filenames.)

Is this new or am I only just now learning of something ISP's have been doing for years?