The title says it all. I was having a conversation with someone about how people generally trust closed source programs, platforms and protocols less than open source ones. He then mentioned banking and said that he thought that banks keep their code under lock and key. I did some googling, but couldn’t find a clear answer. It seems like some banks recently wanted to adopt more open source practices (implying that they were closed before), but not much more.
One thing I thought of is that maybe the protocols would be open, but not the specific implementation for each bank, but I don’t know how I would be able to check that with my current level of knowledge.
So is code for internet banking closed source, and if so why does it seem to be one of the few closed source things that is still trusted?