[leecbaker]

I have heard rumors that they use the TCP TTL field to detect tethering, regardless of device type. If you open a connection from a tethered device, the TTL field will be one count smaller than if the connection originated on the device itself. (This assumes that all devices being used have the same default TTL).

Ref: http://netmgt.blogspot.com/2011/03/detecting-obscuring-tethe...