How does the ebola virus attack?
It is known that Ebola uses at least one cholesterol transporter called "Niemann-Pick C1" (NPC1) to enter its host cells. Cells with a mutated form of this transporter were not infected by the virus (this extends to other viruses from the Filovirus group as well), which seems like a proof that this can make people "immune" to the virus. However, these are only experiments in cell culture. Other experiments show that a small molecule inhibitor that mimics the transporter can inhibit Ebola from entering cells and infecting them. 

There are two papers on this topic:


Ebola virus entry requires the cholesterol transporter Niemann-Pick
C1
Small molecule inhibitors reveal Niemann-Pick C1 is essential for
Ebola virus infection


If a person manages to survive an Ebola infection the immune system fights the virus by making highly specific antibodies against it. These antibodies bind to the viruses and mark them for the immune system (mainly through mast cells) for take-up and degradation while inhibiting them from infecting other cells. Serum from Ebola survivors has been used as experimental treatment for infected people (here mainly the antibodies can be helpful). People who survive the infection are immune against another infection of the same virus strain.