Malware is a type of malicious software that can be used to obtain your sensitive information or delete or modify files. Basically, it can be used for any and all unwanted purposes. The most common types of malware you'll see are viruses, worms, adware, spyware, trojans, rootkits, backdoors, botnets. Oh my. I know it's a long list, but we'll go into detail about each of these and even learn about some real-life cases. But for now, let's talk about the most common forms of malware. Viruses are the best known type of malware. They work the same way that viruses in your body work. When you get sick, a virus attaches itself to a healthy cell in your body, then replicates itself and spreads to other healthy cells in your body until bam, you're sneezing and wheezing and you're a mess. In a computer virus, the virus attaches itself to some executable code like a program. When the program is running, it touches many files, each of which is now susceptible to being infected with the virus. The virus replicates itself on these files, does the malicious work it's intended to do and repeats this over and over until it spreads as far as it can. It's scary. Well, hold on tight. We're just getting started. Worms are similar to viruses, except that instead of having to attach themselves onto something to spread, worms can live on their own and spread through channels like the network. One case of a famous computer worm was the ILoveYou or Love Bug, which spread to millions of Windows machines. The worm was spread via email. Someone would email a message with the subject line of I love you and an attachment that was actually the worm disguised as a love letter text file. The text file was actually an executable file that when opened, would execute many attacks like copying itself to several files and folders, launching other malicious software, replacing files, and then hiding itself after it was done. The worms spread by stealing email addresses that were in the victim's computer and chat clients. It then proceeded to send that email out to everyone in the address book. The Love Bug spread across the world and caused billions of dollars in damage. Not so lovely. This was just one of the many reasons why you should never open email attachments that you do not recognize. Adware is one of the most visible forms of malware that you'll encounter. Most of us see it every day. Adware is just software that displays advertisements and collects data. Sometimes we legitimately download adware. That happens when you agree to the terms of service that allows you to use free software in exchange for showing you advertisements. Other times, it may get installed without your consent and may do other malicious things than just display advertisements. In Greek mythology, there's a famous tale of the evasion of the City of Troy. The Greeks who had been trying to gain access into the walled city, finally decided to hide themselves in a giant wooden statue of a horse under the guise of a gift. The Trojans allowed the gift inside then in the dead of night, the Greeks broke out of the statue and attacked the city. In computer security, we have malware that functions like a Trojan Horse, and it's named after this exact thing. A Trojan is malware that disguises itself as one thing, but does something else. Just like how the historical Trojan Horse was accepted into the city by the citizens of Troy, a computer Trojan has to be accepted by the user, meaning the program has to be executed by the user. No one would willingly install malware on their machine. That's why Trojans are meant to entice you to install them by disguising themselves as other software. Spyware is a type of malware that's meant to spy on you, which could mean monitoring your computer screens, key presses, webcams, and then reporting or streaming all of this information to another party. It's not good. A key logger is a common type of spyware that's used to record every keystroke you make. It can capture all of the messages you type, your confidential information, your passwords, and even more. Ransomware is a type of attack that holds your data or system hostage until you pay some ransom. Our case of ransomware was the WannaCry ransomware attack in May, of 2017. The malware took advantage of a vulnerability in older Windows systems, infecting hundreds of thousands of machines across the world. Most notably, the attacks shutdown the systems for the National Health Services in England, causing a health-related crisis. The WannaCry ransomware attack devastated systems around the world. These types of attacks are becoming more common and we need to be ready to fight them. Let's soldier on.