From GEWar Manual
If two or more alliances in are in a war they usually try to find as much info as they can get about the enemy.
A somewhat popular approach for an alliance is to find a player who spies on the opponent's alliance i.e. tries to join them to take a look at their alliance page, their chats etc to send it to the "employer".
That's of course not forbidden by GEWar rules as long as you are not creating another account to spy or log in as someone else. Doing this would be punished with a ban.
Spying is with no doubt a difficult task, most alliances, in particular the big ones will try to get to know the person who wants to join them and for example ask him a several questions about motives wanting to join this alliance and so on.
In most cases spies will demand some kind of reward for the info provided as they are carrying the biggest risk of being revealed as spy. GEWar is a game where reputation also counts a lot and there are some things the GEWar community never forgets, in particular when the incident is debated in public forums of GEWar and chats. Nevertheless, spying can be a honorable thing to do in the eyes of your 'employer'.