Neutral Party Ships Randomly Apearing At My Planets!

I have just been playing into a game for 6 hours and 3 of my planets (behind many well defended planets) suddenly were under attack by small forces of neutral party ships. The neutral partys attacking each of the 3 planets was very similar to the start game sets. The problem is it was completely out of the blue. They attacked my research stations at these undefended planets. How is this possible?

Just to make the note, I am using the lastest version of entrenchment.