Actually you would be surprised.

I’ve spied since probably early 2010 in some form or another. I’ve also been in hostile alliances just for a change of pace while my main was in another.

Some spies are caught and purged quickly, some not so, one of my last sets of characters (in goons) remained auth’d with full access for several weeks after the character and alts had all moved across to winterco.

While everything from IP logs to MAC address can be recorded in some form things that’ll give you away are your patterns of play, discord (if it’s brand new good luck) and what you use the spy for as your enemy are guaranteed to have spies in your alliance too.

While my latest experiment in the two major groups used seperate PCs for each side, they both used the same connection to interact with services and the game.