How do you verify that nothing has been changed, if not by checking signatures? Your call for everyone to be fired is very much in vogue but perhaps not at all

How do you verify that nothing has been changed, if not by checking signatures? Your call for everyone to be fired is very much in vogue but perhaps not at all useful. This isn’t a great thing to have happened, but the important outcome is, as always, knowledge and process that can prevent similar mistakes in the future.