i was reading the back archives of a canadian privacy law blog, and he linked to a judicial decision. apparently as part of an investigation in which were used yahoo chat and google's old 'hello' image trading program the officer was able to determine a suspect's modem's MAC address: In order to determine who STEPHTOSH was, the officer did a trace on a programme called WHO IS in an effort to learn from where STEPHTOSH was coming. WHO IS is a command program available to the public. The officer was able to ascertain that the person using the name STEPHTOSH was a Rogers Internet customer. The officer was able to obtain the Internet Protocol address, also known as the I.P. There is only one location for an I.P., which is unique to that subscriber. By use of the website known as DNS STUFF.com, one is able to find with which company this I.P. is registered. It was ascertained that the I.P. address used by STEPHTOSH was registered to Rogers Cable, from the Toronto area. The officer also learned the Cable Modem MAC address used by STEPHTOSH. This was all the information the officer was able to amass. now it was my understanding that the MAC address of any given device can only be accessed if you're only one 'hop' away on the Internet. the suspect in question was in Markham and the officer part of the Toronto Police, so it's conceivable that they both might have used Rogers internet. but would that still put them only one 'hop' away from each other? i thought the first hop after the modem was usually the ISP? and if he'd used a netBIOS query against this guy's machine it would return the ethernet card's MAC, not the modem's. so is this guy on the same rogers subnet as the suspect's cable modem, is that functionality part of google's Hello (i could only think that it would be possible if Hello operated as a virtual LAN or something), does the officer have remote access to the arp caches of the routers at Rogers or is he just full of crap and lying to make his case stronger?