-- andr...@fastmail.fm
On Thursday, September 08, 2011 7:32 PM, "Seth David Schoen" <sch...@eff.org> wrote: > Andre Risling writes: > > > I've some questions about MAC address and changing it > > > > - Why would someone want to change ("spoof") their MAC address? > > The MAC address usually identifies a particular physical computer > to a local area network. If someone doesn't want their physical > computer to be recognized by a network, they might want to change > the address. > > The most common reasons for this in practice are probably > > * Some networks let people use the network for free, but only for > a limited period of time, or only on one occasion; this is > enforced using MAC addresses, so changing MAC addresses lets > people get around the restriction and continue using the > network. For example, an airport or university wifi network > might let a "guest" use the network for 30 minutes without > paying or registering. > > * Some networks might ban someone they consider abusive or > unwelcome using the MAC address (for example, an open wifi > network where someone has used it in a way that the operator > considered abusive or excessive). In that case, the person > who was banned might change their MAC address to get around > the ban. > > * ISPs might record or log MAC addresses, which could be used for > commercial or law enforcement purposes, so someone who doesn't > want to end up in such logs might use a false or random MAC > address. In some places, law enforcement might pressure or > require the ISPs to keep these logs as a way of trying to catch > people accused of breaking the law, or as a way of providing > corroborating evidence after-the-fact when a suspect is caught. > > * Although it's not known to happen on a large scale, other people > on a LAN with you could detect and log your MAC address to > monitor when your computer is physically present on the LAN > (perhaps to learn or make a profile of when you're present at > a certain place that you're known to visit periodically?), so > changing your MAC address would let you avoid this kind of > monitoring. > > * Some ISPs use a clumsy policy where the subscriber's observed > MAC address is not allowed to change frequently (sometimes > because of somewhat obsolete ISP billing systems that used the > MAC address to identify the subscriber, or sometimes because > of old ISP policies meant to discourage people from using more > than one computer with a single account). In this case, > people may change the MAC address of one computer (or a wifi > router) to match the address of a different computer (which > is called "cloning"). This could also be used by someone > who has paid for a certain amount of Internet access on a paid > wifi network (say, in an airport or hotel) let a friend take > over using the access when the first person is all done. > > > - Is a computers MAC address sent out whenever you connect to the web? > > > > -If it is, how often is it sent out? > > It's "sent out" to the local router but not out over the Internet, > so web servers, for example, can't observe it. You have to be on > the same LAN in order to observe it. > > > - Who stores the MAC address of the computer you're using? The ISP? An > > Webmail service? > > Whoever operates the local router can store it (e.g., if you're on a > friend's wifi, the friend could store it; if you're on a commercial > wifi network, the commercial wifi operator could store it; if you're > directly plugged into a cable modem owned by an ISP, the ISP could > program the cable modem to store it; ...). > > An exception is that some software could deliberately choose to > transmit the MAC address for its own reasons, like enforcing > anti-copying restrictions or because of a weird choice to use the > MAC address to identify individual computers for some other reason. > There's nothing about how the Internet works that _requires_ any > software to do this, and it's probably not common. > > > -Does the Tor network capture and store Mac addresses? > > Nope, never. > > -- > Seth Schoen <sch...@eff.org> > Senior Staff Technologist https://www.eff.org/ > Electronic Frontier Foundation https://www.eff.org/join > 454 Shotwell Street, San Francisco, CA 94110 +1 415 436 9333 x107 > _______________________________________________ > tor-talk mailing list > tor-talk@lists.torproject.org > https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-talk > Excellent! Thank you for the thorough answers. -- http://www.fastmail.fm - The way an email service should be _______________________________________________ tor-talk mailing list tor-talk@lists.torproject.org https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-talk