[Fyron]

There is not really much you can do to detect (or prevent) "unofficial alliances". You might not ever attack a particular empire because it is never advantageous to do so, and they might not attack you for the same reason. I know I would hate to be accused of having some sort of "unofficial alliance" just because I have not attacked a neighbor.

Also, if two players do form such an alliance, they can stage mock wars and battles just to keep up appearances of not having an alliance.