Private Mode not so Private
Many network students know that IPv4 has a limited number of addresses available for use on the Internet. To remedy the situation, three different IP ranges were reserved for internal use on private networks. To access websites, however, a device needs a public routable IP address. To make Internet resource accessible to computers or devices using private IP ranges a go-between is necessary. We call this go between Network Address Translation (NAT). NAT acts as go between taking requests from the internal private computer and resending the request using the NAT device's public IP address. This means your NAT device needs to be on the internal network and the external network (Internet). It will have an Internal IP address to communicate with devices on the private or internal network. In the example illustrated here, the internal IP address of the NAT device is 192.168.1.255. The external IP address will be assigned by an Internet Service Provider (ISP). In this example, the external IP address is 184.108.40.206.
Some people think opening Firefox or Internet Explorer in privacy mode to browse websites will protect their privacy. Sure there is a level of obscurity obtained by using privacy mode. However, when you navigate to a website, the website needs to respond giving your browser the HTML or other code for you to view in your browser. The site knows the IP address the request came from and will send the request back to the same IP address. Even if you don’t log in to the website they know the request came from your IP address and they can correlate that IP address with other past logins.
The websites may not be able to track the other sites you visit, but they will be able to track your browsing of their site. Your ISP can track all the sites you go to, and there isn’t much you can do to stop that. Well that is for another post!
Why do sites want to track you?
There is big money targeted advertising. People will pay good money to send you ads related to your interests. You are more likely to buy something that is of interest to you. The more they know about your online habits, especially shopping and search history, the more likely you are to respond to their ads.