Not understanding that fundamentally a whitelist is safer and better than a blacklist. I have gotten into many fights about this in my work about this because i

Not understanding that fundamentally a whitelist is safer and better than a blacklist. I have gotten into many fights about this in my work about this because it always leads to a hole later when something new or unknown sticks its head out. If there are ten things it is supposed to be able to do make a list of ten things, don't just try to filter out what might not look like the ten things.