Mac adresse ligger i header på omtrent alle tcp/ip pakker og kan spores opp lett. noe jeg lærte fort på jobben. les litt her så skjønner du litt mer. kjører du backtrack kommer du tilbake til den som startet alt uansett.

The Ethernet MAC address is used for local addressing between your computer's network interface and the other computers and routers on the LAN. As soon as a router accepts a packet and forwards it to the next router upstream, your MAC address is removed and the router's upstream MAC address is used instead. When traffic passes from one type of network to another, e.g. Ethernet LAN to ATM or frame relay, it is not even meaningful to talk about MAC addresses being exchanged.

So, MAC addresses are never used outside the LAN with Internet protocols, though some switched LANs can be rather large, e.g. I've seen entire companies with up to thousands of staff on one switched LAN.

Some application or web applet could conceivably find the local MAC address(es) and embed them into content that is sent over the Internet to a server... I do not know what security protections there are for this in contemporary browsers. What was said above about creating an IPv6 address with your MAC built into it would be an example of this, exposing local MAC addressing more globally than is necessary for Internet communication. There is a convention called "privacy extensions" to actually generate new, unique IPv6 addresses periodically to prevent correlation attacks; this is a luxury now possible with the greatly enlarged IPv6 address space (addresses are no longer a scarcity). However, I am not aware of IPv6 ISPs in Thailand so this all might be a bit academic...

Most likely, a web site tracking you between sessions would be using cookies, storing a unique value in your PC that was provided by the server on the first occasion you accessed the website.