Your browser will send this ID number to the site whenever you visit the site. This will allow the site to recognize you. Old versions of Netscape had bugs that allowed web sites to query your e-mail address. I don't know of any such problems with current versions of web browsers. Firewalls Generally speaking, a fire wall is a device that controls traffic between your computer and the Internet.
Firewalls come in all shapes and sizes.
It is too much for this web site to cover all the ins and outs of firewalls. Mostly used to connect LANs to cable modem. But it will also work as a firewall. Linux can be configured as a firewall. Final Word Be vigilant.