Yeah, that reminds me of this system, 1:444, where a recently inactive player has 8 planets doing nothing. And it seems they hold nothing but resources.
At first, I thought it was because my Espionage levels were too low, that my 8 probes were not enough to detect defenses. But when I finally decided to risk some cargo ships on a couple of those planets, I came back full.
1:444:1, 3, 6, 7, 8, 10, 13, 14 are all owned by the same inactive player. Who wants to help me test each one of these planets over the next couple of days?