you pick up multiple missions from multiple close-by agents and kill only one BS per time. you jump out , go to mission No2, kill 1x BS, jump out, go to mission No3 kill 1 BS..
Trick is, that according to what Defka says, each time you jump a system, your sec. status is updated with the 1 BS kill.. SO you do that all the time, to get faster Sec. status increase