In the 110 years since the Secret Service began protecting the President, only seven assailants have actually reached their target, and only one has accomplished his goal. The Secret Service has maintained this record despite the President meeting tens of thousands of people during his term, and speaking at hundreds of public events every year.
Cybersecurity defenders face a similar problem: they are defending high-value assets that must be protected, but also have to speak to hundreds or thousands of other servers. But our cybersecurity record doesn't look as successful – 2,260 data breaches in 2015 alone, with the majority of intruders taking only minutes to compromise systems, and the majority of defenders taking days to identify a breach.