1. st step : regular HR is checking application formulars and documents you have. They might ask some 2-100 questions you should answer quickly, might also talk in very friendly manner and be really polite.
2. nd step: if technical specialists after meeting with you and discussions about stuff where they need you.... will tell that you are usable, then next step will be 3 rd.
3. rd step : internal security department specialists will do background check...they does have access to some interesting databases and might contact with your previous job administration, education institutions, also check are documents legit or no etc.
4. Th step: if this is passed your background check in depth will be KGB job.
They might check ppl you are living in the same address, family members, close friends background too, contact with your former bosses, tutors, classmates, coursemates, work colleques, neigbours, former landlorlds etc and ask about you...a lot of questions.
Ofc also to check all awailable databases about you.....
In some cases even about your family members, relatives and so on...
# in the end will be decision what level access you should have in best case, how strict will be your monitoring, assesement about risk potential you might have etc....
If you will apply to work in Central Bank of RF checks will be more " soft "....