They were privateers. They attacked pirate ships as their primary prey. However, there were times they attacked civilian vessels as well. However, when they attacked civilian vessels, it was not the outcome people expected. While everyone was unconscious from the knockout gas, they would go around the ship repairing any damage they did, and any issues they noticed, make sure the crew and passengers were unharmed, and then leave a listing right where the captains and crews could find them of where their vulnerabilities are, and how to better prepare should the next attacker be of the unfriendly kind. -- Teachers
It started small, as big things often do. Their usual routine had become almost dull. Step one, sneak up on ship; step two, dock inside their scanner's blind spot; Step three, fill the ship with knockout gas; step four, profit. They freed every slave they found, and took any ill-got gains. Until they tripped over the Grubworm.
It was a low-grade scavenger ship that only turned up on their targeting algorithm because of the large volumes of gold and organic material. What they actually had was a hold full of old wires and terraformable soil. It also had several problems with the engines, life support, and sundry nonsense that included basic defenses. Feeling guilty, the crew of the Manic Liberator set to work while the two crewmembers slumbered safely in their bunk niches.
They fixed up and added variety to the air scrubbing system, including the wick watering system, which was one good sneeze away from total collapse. The repaired the food printer. They added some missing nutrients to the nutrient packs, which had been empty for some significant time. They even left some treats for the ship's cat after stopping to pet the slumbering feline.