Whatever the threat, it is arriving to your computer in one of two ways: human adversary or malware. Human attackers can use any of the hundreds of thousands of known computer exploits and attack methodologies to compromise a computer or device. People are supposed to run patching routines, and many devices and software programs try their best to automatically update themselves, yet many computers and devices are left vulnerable for long periods of time even after the patches are available, a fact that hackers love.

Källa: What hackers do: their motivations and their malware