Early laptop viruses were created for enjoyable, with no malicious intent beyond a simple prank. But now “prankster” malware is vastly outnumbered by malware that causes actual and extreme injury. Botnets aren’t technically malware — they’re networks of contaminated computers that work together under the control of an attacker. Malware is at the root of most cyberattacks, including the large-scale knowledge breaches that lead to widespread identification theft and fraud. Hackers aim malware attacks towards people, firms, and even governments.