@thor i'd really like to have a good source for fil here in germany. we've got all the turkish stuff here which is nice, but fil is more to my liking.
in general, it's pretty interesting which methods of preservation people have come up with in different regions. the bacteria in fil have their optimum temperature at 15-20°C, while for yoghurt it's >30°C. the same for cheeses. traditional food "around the world" is pretty interesting.