http://ask-leo.com/how_can_my_isp_tell_that_im_downloading_copyrighted_files.html
這就因為我的ISP帳號裏唯一的一次非法下載的東西是於6/17/2010下載的”Up In The Air”, 可能是通過運行了P2P共享軟件而遭到ISP警告:嚴管我的家網, 而不是他們聲稱的於5/9/2010下載的"The Hurt Locker".如果再遭一次ISP警告,根據協議他們有權中斷我的網絡服務。
How can my ISP tell that I'm downloading copyrighted files?
ISP can't examine the data, but they can still see where the data is coming and going, and what kind of data it is.
So even encrypted your ISP could still say "hey, you're running peer-to-peer file sharing software, and we don't allow that: knock it off".
Yes, there are attempts to further obfuscate peer-to-peer file sharing traffic, but you get the idea - for the most part even if the ISP can't see what you're sharing, they can see that you're sharing.
And for many, that's enough.