Vulnerability Assessment - When is Enough Enough?

Via Jeremiah Grossman's Blog -

This is a fair and increasingly common question in web application security. Especially considering that we never know how many bugs (or vulnerabilities) actually exist in a piece of code. This is also why I tend to approach security as an attempt to make a system as hard as possible (not impossible, because that’s impossible) for the “bad guys” to break-in. Finding and fixing vulnerabilities, whether pre-deployment or post-production, makes the next vulnerability harder to identify. The idea is to require the bad guys to expend more resources (time, money, etc.) than it’ll be worth should they succeed. Realistically though given a long enough timeline, everyone gets hacked, if they haven’t been so already. Which begs the question, when do we stop looking for vulnerabilities?