You will get credit rewards and reputation bonuses for killing enemies of a faction within range of that faction’s stations. The larger the ship (S/M/L/XL) the higher the reward.
You can check the in-game Encyclopedia, under Factions, to see a list of which factions are considered enemies of the other factions.
Credit is only awarded under specific circumstances:
- you have to be within about 45 km of a station
- your shot has to be the final one that destroys the ship
- the ship you killed is an enemy of the faction that owns the station
If you only help kill a ship, that doesn’t count. If a ship you own but aren’t piloting destroys something, that doesn’t count.
Note that the reward comes from the station, not the owner of the sector. Who owns the sector is irrelevant, and sector owners offer no rewards.
Note also that you get no special credit for defending ships against attackers. Credit is awarded only for kills of a station’s enemies, next to that station. (So, for example, if you come across a group of Xenon attacking a freighter in deep space, saving the freighter won’t gain you any reputation because there are no stations nearby.)