First, you need to understand how Tor works to protect your privacy?
According to Wikipedia:
Tor is free software for enabling anonymous communication. The name is derived from an acronym for the original software project name “The Onion Router“. Tor directs Internet traffic through a free, worldwide, volunteer network consisting of more than seven thousand relays to conceal a user’s location and usage from anyone conducting network surveillance or traffic analysis. Using Tor makes it more difficult for Internet activity to be traced back to the user: this includes “visits to Web sites, online posts, instant messages, and other communication forms”. Tor’s use is intended to protect the personal privacy of users, as well as their freedom and ability to conduct confidential communication by keeping their Internet activities from being monitored.
Does Tor Hide you From Your ISP?
Tor will not hide you from any ISP. The reason is simply that it isn’t designed to do so.
Tor does hide your identity from websites and servers you visit because this is what it was meant to do.
Tor takes your computer’s requests and ships them randomly throughout the world, leaving a sort of mile-long treasure map of IP addresses for people to go through if they want to find you.
Your service provider comes in before that ever happens. The ISP is what connects your computer to that maze of addresses in the first place. It’s like trying to hide a fake passport from the guy that’s selling them.
Fortunately, though all ISP’s keep track of their users, they are forbidden to release that information unless by court order, and their cyber security undoubtedly tops yours or mine. Nothing known by AT&T can be accessed by a hacker or anyone else (unless you commit a felony).
In short, Tor won’t hide you from everything because there are some things it doesn’t need to do (or can’t legally do).
when you connect to an ISP, it allocates you an “IP address” – four numbers separated by dots…like 126.96.36.199 (that’s Google’s IP address).
Your computer has to use that address to talk to the ISP’s computer or there are no communications.
Since every packet that your computer sends to the ISP…or the ISP sends to you…contains that number in the header, it’s trivial for them to know who you are. So there cannot be any degree of anonymity over that last leg.