The Internet Protocol Address, or IP address, is an address everyone must have when they connect to the Internet. It is like the post office, if they didn’t have an address they could not deliver any mail. the same with an Internet router who is sending packets from your computer to some other computer on the Internet. IP addresses are allocated to Internet Service providers around the world.
Is you IP address private? The answer can be complicated. Normally an Internet Service Provider (ISP) like AOL or Comcast has a record of all customers and what IP address was assigned. If the information is requested by the Police or the courts it is normally available for a certain amount of time. It depends on where you live whether this information is private. Court cases in New Jersey say it is private, in Toronto courts say it is not and it often depends on the specific circumstances. The identity of subscriber can normally be traced back to the subscriber much like a phone number can be traced.
Is an IP address “personally identifiable information?” The answer to this can complicated and it depends on a number of factors. The simplest thing to do is to do a “reverse lookup” to see if the site comes back to a domain name. For instance, the ip address of this web site would be “privacy.net” so the owner can easily be identified as the registered owner of privacy.net. It could also come back as “whatever.comcast.net”
A user can go through a “proxy” to hide their IP address. A proxy sits between the user and the Internet and makes all the request for the user. This hides the user’s IP address much like a PO box hides a street address. A proxy can also be used to circumvent web filters.
there is also the Tor network and the “Onion Router.” This works via Peer-to-peer connects in such a way as to try to hide who is actually sending or receiving packets. However, it may be possible to defeat the privacy protections in a number of complicated ways. Again, it depends on the specific circumstances. Using TOR may also trigger alarm bells. For instance, some financial services (such as Mt Gox Bitcoin Exchange) may ban you if your account is accessed via Tor. There are also claims that tracking a package via the Post office via Tor will cause the package to be searched for illegal items.