In Elite Dangerous I picked up a combat mission that was along the lines of:
Go to location X and kill Y number of pirates on behalf of group Z.
I jumped to the necessary system and started checking for ships flying around, any that I scanned and had a 'Wanted' level I would interdict and attack yet it still always said I had 0/Y kills. I even flew back to a station to claim the bounties on the off chance that would update the list, but with no result.
As the instructions didn't specify a particular faction why did the kill levels not increase? Is there anything specific that marks an NPC / player as a pirate and not just a wanted ship?