Use Clear Body Language. If someone is following you closely looking for a place to pass, and you kind of drift along with ambiguous movements about the track, or you sort of close the door but still leave the inside line half open, then you just might unintentionally lure the following car to try a pass that's only half on. Alternatively, if as soon as a following car gets anywhere near your rear quarter coming up to a corner, and while they are still in your mirrors, you make a firm and clear movement towards the inside line, and stick there, then they will know that your intentions are to close the door and drive the defensive inside line. Such a clear defensive move will leave them in no doubt not to try a risky inside pass.
Dang, about 0.3 percent of LFS racers understands that.