After many years of living in bad neighborhoods, I've learned a few things:

1) If someone is determined to rob/attack you, they can/will eventually do it. However...
2) Almost all thieves are lazy, and can be easily discouraged.

The internet is a bad neighborhood, so the same rules apply.
There is no such thing as perfect security, but you can discourage almost everyone who would do you harm.

After many years of working in IT, I've learned a few things: