What about having a mission variable that gets set to true once you have defeated the viper,
You see, here we have exactly the point. There is one viper for every system with a Hacker Outpost in it. Defeating it gives you the code for the Outpost in that specific system
. Why would you expect it to have any effect on finding Outposts in different systems? The hackers are not a corporation, but completely independent of each other.
Therefore I would need one mission_variable for each system with a potential Hacker Outpost in it. Because if you've defeated the viper in Retila, it gives you the direction to the Hacker Outpost in Retila and nothing else. So I would have to store the fact that you know the directions to the Outpost in Retila. If you, later in your game, defeat the viper in Raoror, this fact would have to be stored independently of your success in Retila (both systems in Gal 1). And so on. I don't even know how many Anarchies with the necessary TL exist in the eight galaxies.
I didn't want that. What we could talk about is storing the information for the current system, so that the Outpost would be created again if you quit and reload the game. Problem is: the Outpost is created at a random location within the system, so there would be no guarantee that it would be recreated at the same place.
Thus I prefer to think that the hackers regularly change their codes, and therefore after a while your adcanced space compass doesn't receive their transmission any longer, or something of the like. If that is dissatisfying, please apply Bellisario's Maxim
. And the MST3K Mantra
, of course.