Chapter Six · Malware
Chapter 6: Malware — Hostile Software
Malware is the word for software written to work against you instead of for you. This chapter strips away the mystery: a virus, a worm, a trojan, ransomware — these are all just programs, running like any other, with a hostile job. Once you see them as ordinary software with a bad purpose, both how they work and how they get stopped start to make sense.
The word "virus" gets used for every bad thing that can happen to a computer, and that habit hides more than it reveals. Underneath the scary headlines, malware is not magic and not a glitch — it is software, a program running like any app on the device, written or altered to steal, spy, damage, or hijack. That plain framing is the thread running through the whole chapter.
Four topics build the picture. First, what malware actually is and the two things every piece of it has to do — arrive on a device, and get itself to run. Then the family: virus, worm, trojan, and spyware, told apart by how they spread and what they do. Then ransomware on its own, because it turns a tool for good — encryption — into a weapon. And finally how malware gets in and what it does once it is there, which is exactly what the defenses later in the course are shaped to stop.