From reading a lot of info on this website I came to the conclusion that if someone with enough skill really badly wants to gain access somewhere, then there is absolutely nothing stopping them from doing so. Additionally I learned that getting access to a company computer is much easier than a singular computer at home.
However I am completely confused. What exactly prevents someone from for example, stalking one(or more) of the bank employees, getting information on them and then gaining access into their system? As far as I have seen financial fields have one of the most soul sucking programming tasks which usually end up in small amount of security holes. So what would prevent someone from waltzing into the bank's system, causing gigantic chaos (not for sake of stealing money, but for sake of screwing them up), and then walk out.
For example I know from internal sources that this has one of the worst security methods implemented. This makes me assume that this is not the first software that a bank would release that would allow data to be stolen and/or modified.
Does this actually happen but the banks do not care because they suffer very small damages? Or is a bank completely impossible to get into and destroy data?