[LINK] MAC addresses on public wifi

Kim Holburn kim.holburn at gmail.com
Fri Jul 16 12:03:08 AEST 2010

On 2010/Jul/16, at 11:08 AM, Jan Whitaker wrote:

> Linkers,
> When one uses a public wifi network and gmail, does the header
> contain the MAC address of the device that connected to the network?
> Alternatively, are there any other identifiers in the email or on the
> local network at the wifi point that would tie to a particular piece
> of hardware?

Unless your email server is on the local public wifi connection it  
will never see one's MAC address.  MAC addresses are only local.  Once  
packets leave the local wifi/ethernet, ethernet/MAC addresses are  
stripped and only IP addresses are left.  If the local link has  
private IP addresses they may be stripped too and replaced with the  
wifi system's public IP.

Most email servers preserve the IP addresses of the client that the  
email was sent from.  You can see them in the source of the email  
which has a set of headers which start "Received: "  They have all the  
IP addresses that the servers have seen.

Mail sent from a public wifi system has no real identifying data.  The  
public wifi system may have logs which can identify MAC address with  
local private IP, but it's unlikely.  If it did have police might be  
able to get access or a subpoena.

Kim Holburn
IT Network & Security Consultant
T: +61 2 61402408  M: +61 404072753
mailto:kim at holburn.net  aim://kimholburn
skype://kholburn - PGP Public Key on request

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