This will work short term but if that server in Latvia logs your MAC address they MAY block that and you will not be able to get past it as it is unchangeable, For whatever reason they are kicking you off they can use the IP Database and lookup your IP and it will link to Karoo and they may even contact Karoo and they may kick you off of their network aswel
How does a MAC address get through a series of routers?
This is a good point. Does the WoW client forward the end users' MAC address to the server as part of the game data because I believe the source MAC address assigned to a data packet changes as it is forwarded from router to router in normal use.
The MAC address is stripped off by the routers (not switches or hubs) as they are only needed to get from one physical device to another. Each physical device has its own unique MAC address.
If the software is digging out a PC MAC address and reporting it independantly, it is trivial to change the MAC address of a PC network card with Device Managed in XP.